By ELLEN BARRY
TALLINN — As an independent state emerged here after 47 years of Soviet rule, a jovial, meticulous police official named Herman Simm was promoted again and again. By 2001, he occupied a post that satisfied his fascination with secrets: As chief of the National Security Authority, his job was to secure all classified communication between Estonia and its allies.
And prosecutors say they have established why he was so interested in secrets: They believe he was passing information to an undercover agent for the Russian Foreign Intelligence Service. The contact is identified in documents as “Jesus” and is likely to be a citizen of Portugal, said Mr. Simm’s defense lawyer, Owe Ladva.
Though the authorities have not said when they believe the spying began, Mr. Simm was in place during a critical period, from 2001 to 2006, as Estonia became a member of NATO and Moscow’s frustration at the Western military alliance grew into a hostile standoff. He was arrested in September on suspicion of treason.
The case has unnerved NATO as it prepares to integrate more Eastern European nations once in the grip of Soviet security services. It is a serious blow to Estonia, which has made challenging Russia a central aspect of its political identity. And throughout the region, it has stirred up fears that Russian intelligence networks may survive, in dormant form, even at the highest levels of government.
“The Simm case is a serious sign of the situation in today’s world,” said Jaanus Rahumagi, chairman of the Estonian Parliament’s committee overseeing security services. “While all of Western Europe was looking to the Middle East and Asia, Russia was building up an efficient system in Europe.”
Aleksei Pavlov, a Kremlin spokesman, dismissed the notion that Russia was stepping up spying and said Mr. Simm “never had any connection with any type of Russian government agency.” He added that domestic considerations, including terrorism, were the priority for Russia now.
“It is not exactly the case where we will be activating our international network,” he said.
Mr. Simm is cooperating with Estonian authorities and has offered useful information about modern Russian spying, Mr. Rahumagi said. As for his contact, he said, “the alliance has full control over this person, and I can’t offer more information than that.”
Over recent months, Mr. Simm underwent questioning — without a lawyer present, by his own choice — about people he met with, Mr. Ladva said. He said that his client would not comment on the charges, but that based on his knowledge of Mr. Simm, “it is very difficult to believe that he would plot to do something damaging to Estonia.”
The scope of the damage to NATO and to its member countries is not clear. A team of NATO investigators is at work in Tallinn, Estonia’s capital, trying to determine what information Mr. Simm shared with Russia, said Andres Kahar, a spokesman for Estonia’s security police.
The German magazine Der Spiegel reported this month that Mr. Simm was also selling secrets to the German external intelligence service, the BND, informing on Russian spying in the Baltics.
Mr. Kahar said Mr. Simm lacked access to critical streams of information, including plans for a NATO cyberdefense center based in Estonia, the identity of Estonian and foreign intelligence agents and details about plans for missile defense systems in Poland and the Czech Republic.
A NATO spokesman, James Appathurai, would not speculate on the extent of the damage. The case raises clear issues for the alliance, which recently welcomed Romania and Bulgaria, is preparing to admit Albania and Croatia and may eventually accept Ukraine and Georgia, against Russia’s protests. For years, skeptics have questioned whether former Soviet allies and republics were prepared to safeguard Western intelligence.
Estonia was seen as particularly careful, said Olga Oliker, a senior policy analyst for the RAND Corporation., so much so that in the 1990s the government was made up almost entirely of people in their 30s, who traded jobs back and forth rather than risk admitting officials with Soviet connections.
“The more interesting implication is, what does it mean for all the post-Soviet countries — and even for Russia — that think they have a pretty good handle on who they can trust?” Ms. Oliker said.
Mr. Rahumagi, the chairman of Parliament’s security committee, said this case would be the beginning of a new, more effective era in Estonian security.
“If Russia left here the old K.G.B. connections, they all know these days that they will be recovered, because of Simm,” he said. “The shadow after the Simm case — the shadow is very big.”
A congenial man — the kind who never forgot to bring flowers when women in the office had a birthday — Mr. Simm was among the few officials who survived Estonia’s transition to independence. A graduate of a Soviet police academy in Moscow, Mr. Simm was in his 40s when Estonia left the Soviet Union, noticeably older than most of his government counterparts.
Some saw him as patriotic because of an episode in his past. On May 15, 1990, when a pro-Soviet crowd tried to seize control of the Parliament, Mr. Simm was injured while protecting the building.
After a short stint as chief of Estonia’s police force, Mr. Simm was transferred to the Ministry of Defense. In 2001, he was appointed director of the National Security Authority.
He was known as a stickler for regulations, gravely serious at the hint that a document had gone astray. He frequently told colleagues that he felt he was being followed or listened to.
In 2006, Jurgen Ligi, then the defense minister, removed Mr. Simm from the helm of the National Security Authority, keeping him on as an adviser. Mr. Ligi said he made the decision because he had doubts about Mr. Simm’s “character, profile and ability,” though not his trustworthiness.
Jaak Aaviksoo, the current defense minister, said he believed that Mr. Simm did considerable damage to Estonia. He said the vigorous investigation that led to Mr. Simm’s arrest should enhance Estonia’s international credibility.
Still, he said, the notion of an internal traitor is deeply painful for many who worked alongside Mr. Simm.
“Handling the psychological shock is part of the problem,” Mr. Aaviksoo said. “Restoring the normal working atmosphere is a serious exercise.”