Mehdi Marizad / Fars via AP file

A car that was bombed by two assailants on a motorcycle in Tehran on Jan. 11, killing Iranian nuclear scientist Mostafa Ahamdi Roshan, is removed by a mobile crane. The photo was distributed by the semi-official Iranian photo agency Fars.

By Richard Engel and Robert Windrem
NBC News

Updated: 11:14 a.m. ET -- Deadly attacks on Iranian nuclear scientists are being carried out by an Iranian dissident group that is financed, trained and armed by Israel’s secret service, U.S. officials tell NBC News, confirming charges leveled by Iran’s leaders.

The group, the People’s Mujahedin of Iran, has long been designated as a terrorist group by the United States, accused of killing American servicemen and contractors in the 1970s and supporting the takeover of the U.S. Embassy in Tehran before breaking with the Iranian mullahs in 1980.

The attacks, which have killed five Iranian nuclear scientists since 2007 and may have destroyed a missile research and development site, have been carried out in dramatic fashion, with motorcycle-borne assailants often attaching small magnetic bombs to the exterior of the victims’ cars.

U.S. officials, speaking on condition of anonymity, said the Obama administration is aware of the assassination campaign but has no direct involvement.

The Iranians have no doubt who is responsible – Israel and the People’s Mujahedin of Iran, known by various acronyms, including MEK, MKO and PMI.

“The relation is very intricate and close,” said Mohammad Javad Larijani, a senior aide to Ayatollah Ali Khamenei, Iran’s supreme leader, speaking of the MEK and Israel.  “They (Israelis) are paying … the Mujahedin. Some of their (MEK) agents … (are) providing Israel with information.  And they recruit and also manage logistical support.”

Moreover, he said, the Mossad, the Israeli secret service, is training MEK members in Israel on the use of motorcycles and small bombs.  In one case, he said, Mossad agents built a replica of the home of an Iranian nuclear scientist so that the assassins could familiarize themselves with the layout prior to the attack.

Much of what the Iranian government knows of the attacks and the links between Israel and MEK  comes from interrogation of an assassin who failed to carry out an attack in late 2010 and the materials found on him, Larijani said. (Click here to see a video report of the interrogation shown on Iranian televsion.)

The U.S.-educated Larijani, whose two younger brothers run the legislative and judicial branches of the Iranian government, said the Israelis’ rationale is simple. “Israel does not have direct access to our society. Mujahedin, being Iranian and being part of Iranian society, they have … a good number of … places to get into the touch with people. So I think they are working hand-to-hand very close.  And we do have very concrete documents.”

Two senior U.S. officials confirmed for NBC News  the MEK’s role in the assassinations, with one senior official saying, “All your inclinations are correct.” A third official would not confirm or deny the relationship, saying only, “It hasn’t been clearly confirmed yet.”  All the officials denied any U.S. involvement in the assassinations. 

As it has in the past, Israel’s Foreign Ministry declined comment. Said a spokesman, "As long as we can't see all the evidence being claimed by NBC, the Foreign Ministry won't react to every gossip and report being published worldwide."

For its part, the MEK pointed to a statement calling the allegations “absolutely false.” 

Response to article from the National Council of Resistance of Iran

Ali Safavi, a long-time representative of the MEK, underscored the denial after publication of this article,

"There has never been and there is no MEK member in Israel, period," he said. "The MEK has categorically denied any involvement. The idea that Israel is training MEK members on its soil borders on perversity. It is absolutely and completely false."

The sophistication of the attacks supports the Iranian claims that an experienced intelligence service is involved, experts say. 

In the most recent attack, on Jan. 11, 2012, Mostafa Ahamdi Roshan died in a blast in Tehran moments after two assailants on a motorcycle placed a small magnetic bomb on his vehicle. Roshan was a deputy director at the Natanz uranium enrichment facility and was reportedly involved in procurement for the nuclear program, which Iran insists is not a weapons program.

Previous attacks include the assassination of Massoud Ali-Mohammadi, killed by a bomb outside his Tehran home in January 2010, and an explosion in November of that year that took the life of Majid Shahriari and wounded Fereydoun Abbasi-Davani, who is now the head of Iran’s Atomic Energy Organization.

In the case of Roshan, the bomb appears to have been a shaped charge that directed all the explosive power inside the vehicle, killing him and his bodyguard driver but leaving nearby traffic unaffected.

Although Roshan was directly involved in the nuclear program, working at the huge centrifuge facility between Tehran and Qom, Iran’s religious center, at least one other scientist who was killed wasn’t linked to the Iranian nuclear program, according to Larijani.

Speaking of bombing victim Ali-Mohammadi, whom he described as a friend, Larijani told NBC News, “In fact this guy who was assassinated was not involved in the nitty-gritty of the situation.  He was a scientist, a physicist, working on the theoretically parts of nuclear energy, which you can teach it in every university. You can find it in every text.”

“This is an Israeli plot.  A dirty plot,” Larijani added angrily. He also claimed the assassinations are not having an effect on the program and have only made scientists more resolute in carrying out their mission.

Not so, said Ronen Bergman, an Israeli commentator and author of “Israel’s Secret War with Iran” and an upcoming book tentatively titled, “Mossad and the Art of Assassination.”

Bergman said the attacks have three purposes, the most obvious being the removal of high-ranking scientists and their  knowledge. The others:  forcing Iran to increase security for its scientists and facilities and to spur “white defections.” 

He explained the latter this way: “Scientists leaving the project, afraid that they are going to be next on the assassination list, and say, ‘We don't want this.  Indeed, we get good money, we are promoted, we are honored by everybody, but we might get killed.  It isn't worth it.  Maybe we should go back to teach … in a university.’”

There are unconfirmed reports in the Israeli press and elsewhere that Israel and the MEK were involved in a Nov. 12 explosion that destroyed the Iranian missile research and development site at Bin Kaneh, 30 miles outside Tehran.  Among those killed was Maj. Gen. Hassan Moghaddam, director of missile development for the Revolutionary Guard, and a dozen other researchers. So important was Moghaddam that Ayatollah Khamenei attended his funeral. 

Unlike the assassinations, Iran claims the missile site explosion was an accident; the MEK, meanwhile, trumpeted it but denied any involvement. 

Indeed, there may be other covert operations carried out either by Israel acting alone or in concert with others, according to Bergman.

“Two labs caught fire,” said Bergman, enumerating the attacks. “Scientists got blown up or disappeared.  A missile base and the R&D base of the Revolutionary Guard exploded some time ago, with the director of the R&D division of the Revolutionary Guard being killed along with … his soldiers.” 

Bergman added, “So, a long series of … something that was termed by an Israeli (Cabinet) minister … as ‘mysterious mishaps’ happening and rehappening to the project. Then the Iranians claim, ‘This is Israeli Mossad trying to sabotage our attempts to be a nuclear superpower.’”

Dr. Uzi Rabi, director of the Dayan Center at Tel Aviv University, said the supposed accidents could all be part of “psychological warfare” conducted against Iran. “It seems logical. It makes sense,” he said of possible MEK involvement, “and it’s been done before.”

Rabi, who regularly briefs Israel’s parliament, the Knesset, on Iran also said the ultimate goal of the range of covert operations being carried out by Israel is “to damage the politics of survivability … to send a message that could strike fear into the rulers of Iran.”

For the United States, the alleged role of the MEK is particularly troublesome.  In 1997, the State Department designated it a terrorist group, justifying it with an unclassified 40-page summary of the organization’s  activities going back more than 25 years.  The paper, sent to Congress in 1994, was written by Wendy Sherman, now undersecretary of state for political affairs and then an aide to Secretary of State Madeleine Albright.

The report, which was obtained by NBC News, was unsparing in its assessment. “The Mujahedin  (MEK) collaborated with Ayatollah Khomeini to overthrow the former shah of Iran,” it said. “As part of that struggle, they assassinated at least six American citizens, supported the takeover of the U.S. embassy, and opposed the release of the American hostages.”  In each case, the paper noted, “Bombs were the Mujahedin's weapon of choice, which they frequently employed against American targets.”

“In the post-revolutionary political chaos, however, the Mujahedin lost political power to Iran's Islamic clergy. They then applied their dedication to armed struggle and the use of propaganda against the new Iranian government, launching a violent and polemical cycle of attack and reprisal."

Sean Gallup / Getty Images file

Maryam Rajavi, president of the National Council of Resistance of Iran, greets several hundred Iranian expatriates who had gathered to welcome her at Tegel Airport in Berlin, Germany, on March 22, 2010.

U.S. officials have said publicly that the information contained in the report was limited to unclassified material, but that it also drew on classified material in making its determination to add the MEK to the U.S. list of terrorist organizations. 

The MEK and its sister organizations have since the beginning been run by Massoud and Maryam Rajavi, a husband-wife team who have maintained tight control despite assassination threats and internal dissent. Massoud Rajavi, 63, founded the MEK, but since the U.S. invasion of Iraq has taken a backseat to his wife.

The State Department report describes the Rajavis as  “fundamentally undemocratic” and “not a viable alternative to the current government of Iran.”

One reason for that is the MEK’s close relationship with Saddam Hussein, as demonstrated by this 1986 video showing the late Iraqi dictator meeting with Massoud Rajavi. Saddam recruited the MEK in much the same way the Israelis allegedly have, using them to fight Iranian forces during the Iran-Iraq War, a role they took on proudly.  So proudly, they invited NBC News to one of their military camps outside Baghdad in 1991.

“The National Liberation Army (MLA), the military wing of the Mujahedin, conducted raids into Iran during the latter years of the 1980-88 Iran-Iraq War,” according to the State Department report. The NLA's last major offensive reportedly was conducted against Iraqi Kurds in 1991, when it joined Saddam Hussein's brutal repression of the Kurdish rebellion. In addition to occasional acts of sabotage, the Mujahedin are responsible for violent attacks in Iran that victimize civilians.”

“Internally, the Mujahedin run their organization autocratically, suppressing dissent and eschewing tolerance of differing viewpoints,” it said. “Rajavi, who heads the Mojahedin’s political and military wings, has fostered a cult of personality around himself.”

The U.S. suspicion of the MEK doesn’t end there. Law enforcement officials have told NBC News that in 1994, the MEK made a pact with terrorist Ramzi Yousef a year after he masterminded the first attack on the World Trade Center in New York City.  According to the officials, who spoke on condition of anonymity, Yousef built an 11-pound bomb that MEK agents placed inside one of Shia Islam’s greatest shrines in Mashad, Iran, on June 20, 1994.  At least 26 people, mostly women and children, were killed and 200 wounded in the attack.

That connection between Yousef, nephew of 9-11 mastermind Khalid Sheikh Mohammad, and the MEK was first reported in a book, “The New Jackals,” by Simon Reeve. NBC News confirmed that Yousef told U.S. law enforcement that he had worked with the MEK on the bombing.

In recent years, the MEK has said it has renounced violence, but Iranian officials say that is not true, that killings of Iranians continue.  Still, through some deft lobbying, the group has been able to get the United Kingdom and the European Union to remove it from their lists of terrorist groups. 

The alleged involvement of the MEK in the assassinations of Iranian nuclear scientists provides the U.S. with a cloak of deniability regarding the clandestine killings. Because the U.S. has designated the MEK as a terrorist organization, neither military nor intelligence units of the U.S. government, can work with them.  “We cannot deal with them, “ said one senior U.S. official. “We would not deal with them because of the designation.”

Iranian officials initially accused the Israelis and MEK of being behind the attacks, but they have since added the CIA to the list. Three days after the Jan. 11, 2012, bombing in Tehran that killed Roshan, the state news agency IRNA reported that Iran’s Foreign Ministry had sent a diplomatic letter to the U.S. claiming to have “evidence and reliable information” that the CIA provided “guidance, support and planning” to assassins directly involved in the attack.  

U.S. Secretary of State Hillary Clinton  immediately denied any connection to the killings. “I want to categorically deny any United States involvement in any kind of act of violence inside Iran,” Clinton told reporters on the day of the attack.

But at least two GOP presidential candidates have no problem with the targeting of nuclear scientists.  In a November debate, former House Speaker Newt Gingrich endorsed “taking out their scientists,” and former Pennsylvania Sen. Rick Santorum called it, ”a wonderful thing.”

The MEK’s opposition to the Iranian government also has recently earned it both plaudits and support from an odd mix of political bedfellows.

A group of former Cabinet-level officials have joined together to support the MEK’s removal from the official U.S. Foreign Terrorist Organization list, even taking out a full-page ad last year in the New York Times calling for the removal of the MEK from the U.S. terrorist list.  Former Vermont Gov. Howard Dean, former U.S. Attorney General Michael Mukasey, former U.N. Ambassador John Bolton; former Homeland Security Secretary Tom Ridge, former FBI Director Louis Freeh and former Rep. Patrick Kennedy were among those whose signatures were on the ad.

“There’s an extraordinary group of bipartisan or even apolitical leaders, military leaders, diplomats, the United States … the United Kingdom, the European Union, even a U.S. District Court in Washington, said that this group that was put on the foreign terrorist organization watch list in 1997 doesn’t deserve to be there,” Ridge said in November on “The Andrea Mitchell Show” on MSNBC TV.

U.S. politicians also have been pushing the U.S. government to protect the 3,400 MEK members and their families at Camp Ashraf in Iraq, about 35 miles north of Baghdad.  With the departure of U.S. troops, the MEK feared that Iraqi forces, with encouragement from Iran, would attack the camp, leading to a bloodbath. At the last minute, however, agreement was brokered with the United Nations that would permit the MEK members’ departure for resettlement in unspecified democratic countries.  As of this week, there’s been little movement on the planned resettlement.

Jassim Mohammed / AP file

Iranian fighters with the National Liberation Army, the military wing of the MEK, clean armored personnel carriers in 1997 after a field exercise near Camp Ashraf in Iraq.

The Iranians see what’s happening as terrorism and hypocrisy by the United States.  They have forwarded documents and other evidence to the United Nations – and directly to the United States, they say. 

“I think this is very cynical plan.  This is unacceptable,” said Larijani. “This is a bad trend in the world.  Unprecedented.  We should kill scientists … to block a scientific program?  I mean this is disaster!”

Daniel Byman, a professor in the School of Foreign Service at Georgetown University and also a senior fellow with the Saban Center for Middle East Policy at the Brookings Institution, said that if the accounts of the Israeli-MEK assassinations are accurate, the operation borders on terrorism.

“In theory, states cannot be terrorist, but if they hire locals to do assassinations, that would be state sponsorship,” said Byman, author of the recent book, “A High Price: The Triumphs and Failures of Israeli Counterterrorism.” “You could argue that they took action not to terrorize the public, the purpose of terrorism, but only the nuclear community.  An argument could also be made that degrading the program means that you don’t have to take military action and thus, this is a lower level of violence and that really these are military targets, where normally terrorist targets are civilians.”

But ultimately, Byman said, there is a “spectrum of responsibility” and that Israel is ultimately responsible.

Ronen Bergman, while not speaking on behalf of the Israeli government, suggests that there is a justification, citing an oft-repeated but disputed quote in which Iranian President Mahmoud Ahmadinejad’s said that Israel should be wiped off the face of the earth.

“Meir Degan, the chief of Mossad, when he was in office, hung a photograph behind him, behind the chair of the chief of Mossad,” notes the Israeli commentator.  “And in that photograph you see -- an ultra-orthodox Jew -- long beard, standing on his knees with his-- hands up in the air, and two Gestapo soldiers standing -- beside him with guns pointed at him.  One of -- one of them is smiling.

“And Degan used to say to his people and the people coming to visit him from CIA, NSA, et cetera, ‘Look at this guy in the picture. This is my grandfather just seconds before he was killed by the SS,’” Bergman said. “’… We are here to prevent this from happening again.’"

Richard Engel is NBC News' chief foreign correspondent; Robert Windrem is a senior investigative producer.

Brown Harris Stevens

A living room in the combined apartments. The buyer will be one floor below the mysterious apartment of heiress Huguette Clark.

NEW YORK — Curiosity seekers hoping for a glimpse of the New York apartment of the reclusive heiress Huguette Clark will have to make do for now with an extraordinary apartment for sale just one floor below hers in the same elegant co-op. The 18-room, 6,500-square-feet apartment, on the market for $25 million, will be created by combining the seventh-floor apartments of three owners at 907 Fifth Avenue, the historic building at 72nd Street overlooking Central Park's model boat pond.

Even at that size, the apartment would be dwarfed by the property of Clark, the late copper heiress, who has been the subject of a series of reports on msnbc.com about her vacant properties and the management of her fortune. When she died last May, she owned three apartments at 907 Fifth Avenue, with a total of 42 rooms. Two of her apartments make up the entire eighth floor, or about 10,000 square feet, with another 5,000 in an apartment that occupies half of the top floor, the 12th. It's estimated that in today's market her three apartments would sell for roughly $70 million. Though a court fight has begun over her $400 million estate, the executor could choose to sell the Clark apartments soon, perhaps this year.

As The New York Times tells it, "Mr. Carpenter, who was described as 'the father of the modern large apartment' in New York City, was one of the building’s first residents. In the 1920s, he lived alongside oil barons, a tinplate king, a president of the New York Stock Exchange, and a Russian prince."

Martha Stewart, the design entrepreneur, also has an apartment in the building.

Brown Harris Stevens

The library in the combined apartments.

Brown Harris Stevens

A living room in the combined apartments offers a view of Central Park. One can see all the way from Central Park South to, at the north, glimpses of the George Washington Bridge.

Many of the apartments at 907 were eventually subdivided into smaller units. The combination will put three of those back together roughly as originally designed, replacing the servants area with more modern bedrooms. Two kitchens would need to be removed, and air conditioning installed. The new owner would face a co-op fee, including upkeep and taxes, of $12,618 a month, or $151,416 a year. (The Clark apartments cost her $28,500 a month, or $342,000 a year, while she lived for two decades in New York hospital rooms.)

A proposed floor plan for the three apartments.

Those prices bring apartments with light and high ceilings virtually unknown in the city. Guests enter the limestone building through a canopy-protected doorway on 72nd Street into a lobby with a coffered ceiling and a striking stone staircase. Amenities include full-time doormen, a full gymnasium and a landscaped rooftop garden.

You can see the real estate listing and more photos of the apartments here on the site of the real estate agent, John Burger of Brown Harris Stevens.

Previous stories in the Huguette Clark mystery series on msnbc.com:

Archive of all stories, photos and videos.

Photo narrative, "The Clarks: An American story of wealth, scandal and mystery," Feb. 26, 2010.

Printable version of the photo narrative, Feb. 26, 2010.

Clark family notes and sources, Feb. 26, 2010.

Investigative report, part one, "At 104, the mysterious heiress Huguette Clark is alone now: Relatives are kept away. Only her accountant and attorney visit. Who protects HuguetteClark, with 3 empty homes and no heirs?" Aug. 19, 2010.

Investigative report, part two, "Who is watching Huguette Clark's millions? Reclusive heiress's assets are sold by two advisers, one an accountant with a felony conviction. Another elderly client signed over his property to the same accountant and attorney," Aug. 20, 2010.

"Criminal probe begins into the finances of reclusive heiress Huguette Clark: Manhattan DA's Elder Abuse Unit is on the case. The same unit prosecuted the Brooke Astor case; Clark has about four times the wealth," Aug. 24, 2010.

"Report sparks welfare check on heiress Huguette Clark," Aug. 25, 2010.

"Generosity of an heiress: four homes for a nurse, gifts for attorney's family," Sept. 1, 2010.

"Huguette Clark, the reclusive heiress, has signed a will, attorney says," Sept. 2, 2010.

"Family of copper heiress asks court to protect her from attorney, accountant," Sept. 3, 2010.

"Attorney for 104-year-old heiress defends his handling of her finances," Sept. 7, 2010.

"Judge leaves pair under investigation in control of heiress Huguette Clark's fortune," Sept. 9, 2010.

"Huguette Clark, the reclusive copper heiress, dies at 104," May 24, 2011.

"Family excluded from Huguette Clark burial," May 26, 2011.

"Heiress Huguette Clark's will leaves $1 million to advisers," June 22, 2011.

"The 1 percent of the 1 percent: How Huguette Clark's millions were spent," Nov. 19, 2011.

"A $400 miillion twist: Huguette Clark signed two wills, one to her family," Nov. 28, 2011.

"Tax fraud alleged in estate of heiress Huguette Clark; accountant resigns," Dec. 21, 2011.

"Nurse, in line to inherit millions, battles family of heiress Huguette Clark," Dec. 22, 2011.

"Judge bounces attorney and accountant from estate of heiress Huguette Clark," Dec. 23, 2011.

Book coming on reclusive heiress Huguette Clark and her family," Feb. 3, 2012.

Most of the officials said it is highly unlikely that the war-weary U.S. would mount a military attack on Iran, instead relying on financial sanctions and diplomatic pressure to squeeze Tehran. 

Jacquelyn Martin / Pool via Getty Images

U.S. Defense Secretary Leon Panetta speaks with reporters Thursday in Brussels, Belgium, after the conclusion of a day of meetings with fellow NATO defense officials.

Associated Press

Huguette in her last published photograph, in 1930, on the day of her divorce in Reno, Nevada. The heir to a copper fortune died in 2011 at 104.

A nonfiction book on the mysterious heiress Huguette Clark and her family is being written by an NBC News reporter and one of Clark's cousins.

Ballantine Bantam Dell, a division of Random House Publishing Group, has acquired "Empty Mansions," by Bill Dedman and Paul Clark Newell Jr.

Bill Dedman is a Pulitzer Prize-winning reporter for NBC News who introduced the public to heiress Huguette Clark and her empty mansions through his series of narratives on NBCNews.com and NBC's TODAY Show. He lives in suburban Connecticut, where he discovered the first of Clark's three vacant palaces. His narratives on the Clark family have been the most popular story in the history of NBCNews.com, topping 100 million page views. He received more than 1,000 letters and emails from readers of the Clark series, many of them confessing to an obsession with the mystery heiress. As a young woman in New York, actress Kimberly Belflower, explained to her Twitter followers: "Don't mind me, I'll just be reading about Huguette Clark for the rest of my life."

Paul Clark Newell Jr., a grandnephew of W.A. Clark, has researched the family history for 20 years, gathering a unique collection of Clark family photographs, letters and memoirs. He shared many conversations with Huguette Clark about her life and family, and accepted her invitation for a rare private tour of Bellosguardo, her $100 million oceanfront estate in Santa Barbara, Calif. A grandson of W.A. Clark's sister, Newell is Huguette Clark's cousin, not a descendant of her father, and he therefore is not a party to the legal action by relatives to inherit her fortune. He lives in the mountains of San Diego County, Calif.

Executive Editor Pamela Cannon made the deal for North American rights with agent Michael Carlisle of Inkwell Management.

Though she inherited one of the great mining fortunes of the 19th century, Huguette Marcelle Clark lived quietly into the 21st century, secluded under fake names in hospital rooms for more than two decades. Intensely shy, she was almost entirely alone. One of her attorneys represented her for 20 years without meeting her face to face, instead talking to her through a closed door.

Her father, William Andrews Clark, was one of the Copper Kings of Montana and a controversial U.S. senator, believed to be as wealthy as John D. Rockefeller in his day but largely forgotten since his death in 1925.

His youngest daughter, the reclusive heiress Huguette, became a well-known name again in the last year of her life, after her three empty mansions and sales of her personal property drew the attention of investigative reporter Dedman. Clark soon became a subject of public fascination, a trending topic of searches on Google and Yahoo, with fan pages on Facebook, though the last published photograph of her was made in 1930.

When she died in May 2011 at age 104, her obituary appeared on the front page of The New York Times. A legal battle has begun for her $400 million fortune, even as criminal investigations continue of the men who managed her money.

Previous stories in the Huguette Clark mystery series on NBCNews.com:

Archive of all stories, photos and videos

Photo narrative, "The Clarks: An American story of wealth, scandal and mystery," Feb. 26, 2010.

Printable version of the photo narrative, Feb. 26, 2010.

Clark family notes and sources, Feb. 26, 2010.

Investigative report, part one, "At 104, the mysterious heiress Huguette Clark is alone now: Relatives are kept away. Only her accountant and attorney visit. Who protects HuguetteClark, with 3 empty homes and no heirs?" Aug. 19, 2010.

Investigative report, part two, "Who is watching Huguette Clark's millions? Reclusive heiress's assets are sold by two advisers, one an accountant with a felony conviction. Another elderly client signed over his property to the same accountant and attorney," Aug. 20, 2010.

"Criminal probe begins into the finances of reclusive heiress Huguette Clark: Manhattan DA's Elder Abuse Unit is on the case. The same unit prosecuted the Brooke Astor case; Clark has about four times the wealth," Aug. 24, 2010.

"Report sparks welfare check on heiress Huguette Clark," Aug. 25, 2010.

"Generosity of an heiress: four homes for a nurse, gifts for attorney's family," Sept. 1, 2010.

"Huguette Clark, the reclusive heiress, has signed a will, attorney says," Sept. 2, 2010.

"Family of copper heiress asks court to protect her from attorney, accountant," Sept. 3, 2010.

"Attorney for 104-year-old heiress defends his handling of her finances," Sept. 7, 2010.

"Judge leaves pair under investigation in control of heiress Huguette Clark's fortune," Sept. 9, 2010.

"Huguette Clark, the reclusive copper heiress, dies at 104," May 24, 2011.

"Family excluded from Huguette Clark burial," May 26, 2011.

"Heiress Huguette Clark's will leaves $1 million to advisers," June 22, 2011.

"The 1 percent of the 1 percent: How Huguette Clark's millions were spent," Nov. 19, 2011.

"A $400 miillion twist: Huguette Clark signed two wills, one to her family," Nov. 28, 2011.

"Tax fraud alleged in estate of heiress Huguette Clark; accountant resigns," Dec. 21, 2011.

"Nurse, in line to inherit millions, battles family of heiress Huguette Clark," Dec. 22, 2011.

"Judge bounces attorney and accountant from estate of heiress Huguette Clark," Dec. 23, 2011.

It should be clear by now that nothing online is sacred, and no security company is safe from hackers. VeriSign Inc., the firm at the center of so many critical systems on the Web, was infiltrated by hackers in 2010.  Because details of the attack, first disclosed Thursday by Reuters, are so vague we are left to assume the worst -- and the worst is pretty bad.

It's possible that the VeriSign hackers could turn the Web upside down and create an Internet where nothing would be what it seems.  A hacker website could look and act just like your bank's website. Your PC could easily be tricked into downloading automatic software updates that would appear authentic but actually contain viruses. And no matter what web address you typed into your browser, you could be redirected to a criminal's website half-way around the world.

But there's important context to this story which might ratchet down the "Oh My God!" factor considerably.  For starters, there is reason to believe that VeriSign's revelation is nothing more than evidence companies are starting to comply with rules forcing them to disclose such incidents: In other words, similar successful hacks like this may have occurred in the past but simply went unreported.  We'll discuss the evidence for that in a moment. First, let's look at the possibilities raised by the VeriSign attack.

VeriSign is involved in two distinct, fundamental Internet security structures that could be impacted by this attack.  A successful attack on one would be serious, but a raid on the other could threaten the Internet itself. So let's start there.

VeriSign's most critical function is its role in the Domain Name System address book, which governs what happens when Web users type common name Web addresses into their browsers.  There are 13 "root"  DNS servers placed strategically around the planet for redundancy. VeriSign operates two of them. Should a hacker gain access to this part of VeriSign's business, he or she could theoretically poison the other 11 root DNS servers, and the bad data would eventually spread to the other DNS servers. The consequences could be dire: It could mean that everyone who typed "msnbc.com" into a Web browser would be sent to a computer controlled by criminals, instead of the real msnbc.com website.  A computer criminal with destructive intensions could theoretically ruin the database that maps names with IP addresses and effectively shut down parts of the Internet. It has long been discussed that these root name servers are perhaps the most vulnerable point of the attack on the Internet

But it's more likely that the agencies controlling the other 11 root Domain Name Servers would be able to regain control of the DNS table and restore the system within a day or two, if not within hours. As you might imagine, root DNS servers do disagree from time to time and there is a process for handling that.

It's also important to note that VeriSign, in the SEC disclosure which started this incident, claims that its DNS servers were not attacked by hackers.

"Access was gained to information on a small portion of our computers and servers. We have investigated and do not believe these attacks breached the servers that support our Domain Name System ("DNS") network," the firm wrote in the filing.

VeriSign's other crucial function is issuing digital certificates through its VeriSign Authentication Services group. Certificates impact your computer use every day because they tell your PC that a company's website or software is really what is says it is. Certificates are a crucial part of the SSL system that ultimately displays a friendly looking lock when you visit your online bank.  They also identify the legitimacy of software updates sent to your computer by software makers.  Many modern PCs won't install software unless it is digitally signed. 

A hacker who could influence the way VeriSign issues certificates would be a massive problem for both consumers and corporations.

"VeriSign is one of the most important enterprise trust authorities in the world, which delivers people safely to more than half the world's websites,” wrote Catalin Cosoi, Chief Security Researcher at Bitdefender Labs. “A certificate issued by VeriSign will automatically be accepted by both browsers and operating systems. This kind of incident practically voids all the security provided by 64-bit operating systems,"

In other words, hackers would have an easy time loading viruses onto PCs around the world.

That's terrible, but it's not new. Virus writers have been compromising certificate issuers with abandon for the past 18 months. It's one of the reasons that Stuxnet computer virus managed to infect millions of PCs worldwide.  That also means structures are in place to deal with fraudulent certificates.

"The worst case scenario would be several phishing attacks with valid certificates that browsers will render as legit," Cosoi said. "This would potentially yield a huge level of data that could be exploited for financial gain. However, it’s important to remember that a strong anti-phishing solution will keep you protected."

Of course, it's not even clear from VeriSign's filing that its certificate business was compromised.  Complicating matters further: Symantec Corp. purchased most of that business from VeriSign last year. For its part, Symantec said on Thursday that the assets it acquired in the sale were not compromised.

"We want to make it very clear that Symantec takes the security and proper functionality of its solutions very seriously. The Trust Services (SSL), User Authentication (VIP) and other production systems acquired by Symantec were not compromised by the corporate network security breach mentioned in the VeriSign, Inc. quarterly filing," said Symantec spokeswoman Nicole Kenyon in a statement to msnbnc.com.

Of course, it’s possible that one of Verisign’s other business unit – it provides extensive security consulting, for example – was the hackers’ only target.  That seems unlikely, however, given the target-rich environment the offers to computer criminals.

To be sure, many experts think the Verisign attack is serious business.

"The SEC filing says 'Information stored on the compromised corporate systems was exfiltrated.' That sounds like a targeted attack to me," said Mikko Hypponen, chief technology officer at F-Secure.com. "Like the one against Google. And RSA. And Lockheed-Martin."

But it's possible the VeriSign admission, buried in the SEC filing, is little more than paperwork which puts in print something that security professionals have long understood: No firm is safe from hackers.  This might be at once comforting and disturbing: In October of last year, the SEC issued guidelines that called out public firms for under-disclosing security leaks and hinted strongly that fines would come when firms failed to report successful hacker attacks. The VeriSign quarterly report was issued soon after, and it's easy to imagine the disclosure is more routine than anyone would like to admit.  In fact, Stewart Baker, a lawyer at Steptoe & Johnson, predicted as much in a blog earlier this month.

"With enforcement so easy, and the harm from breaches so tangible, so serious and so likely to bring headlines, no one should expect the enforcers to go easy on companies that have been slow to disclose. Instead I expect a growing wave of cases based on companies' failure to make timely disclosure of ongoing breaches," he wrote.

Clearly, admission by VeriSign that executives at the firm were unaware of the breach shows a terrible lack of coordination inside the firm. And it's scary to read this admission, too: "Given the nature of such attacks, we cannot assure that our remedial actions will be sufficient to thwart future attacks or prevent the future loss of information."

Still, it’s important to note that we are talking about attacks that could be a year old, and whatever they were, criminals are already deep in the process of exploiting them. Sad to say there’s nothing most consumers can do in response to this report.

In health news, there’s always the complicated issue of increased diagnosis vs. increased incidence. Is a new disease on the rise, or are we simply better at finding cases of it? The VeriSign incident raises the same question.

But the deeper truth here is probably something that professionals have known for some time: In the cat and mouse game between hackers and security firms, hackers are winning and, in some places, it's starting to look like a blowout.  

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