Different name, same old tricks? The near-unanimity with which the world concluded that Russia's security services were behind the poisoning of Aleksander Litvinenko suggests that the reputation of the KGB has not been erased by renaming it the FSB. And there is plenty of historical evidence that, whatever the name, the organisation's tactics change very slowly.
After 1917, the Cheka - and later the OGPU and the NKVD - terrorised Russians who fled abroad. The thousands who settled in Paris in the 1920s lived in constant fear of murders and kidnappings by Red agents; propaganda from the Kremlin spread the message that no one was safe from its tentacles. Even seemingly committed anti-Bolsheviks among the emigres were blackmailed or bribed into switching sides, and many were turned into agents of the Red terror. One of the most poignant cases concerned the husband of Marina Tsvetaeva, one of the century's greatest poets. Sergei Efron had been a commander in the counter-revolutionary White Army, but in the 1930s sickness in exile led him to accept an offer of safe passage back to Russia on condition that he take part in an NKVD plot to murder a Bolshevik defector. He did so. But when he and Tsvetaeva were taken back to Moscow, it was only for him to be arrested and shot and Marina to hang herself in despair.
The KGB and its predecessors were careful to cover their tracks, though, and always denied responsibility for crimes abroad, even when their fingerprints were clearly visible. They took 50 years to admit it was one of their agents who murdered Trotsky in 1940.
For 10 years after the fall of Communism in 1991, it seemed the organisation had finally been brought to heel, with Boris Yeltsin announcing it had been reoriented towards commercial purposes. But there were growing signs that the FSB reverted to type soon after Vladimir Putin, a former security officer himself, became president. His post-election speech to his former colleagues was widely reported to have begun with the supposedly joky line, "Congratulations, comrades. Our infiltration of power is now complete!"
Certainly, the past few years have seen a dramatic increase in the number of politicians and journalists being murdered in Russia itself. Most of them, like the tremendously brave Anna Politkovskaya, had infuriated the Kremlin by criticising it for corruption or human rights abuses. In virtually all cases, the Kremlin has used the state-controlled media to spread the message that it was not to blame: the usual gambit is to suggest the victims brought it on themselves by being mixed up in shady business dealings or espionage. In Politkovskaya's case, the claims that she was probably assassinated by the CIA were laughable. But the Kremlin seems to be at it again: the Moskovsky Komsomolets newspaper, which has close links to the FSB, has suggested Litvinenko may have been poisoned by the Americans. And the Moscow rumour mill has been copiously fed over the past few days with stories that the deed was done by enemies of Putin in order to discredit him in the eyes of the world: why else, goes the line, would the operation have been carried out with so many hallmarks of an FSB sting? (That question may suggest some desperation in the FSB's PR department.)
The use of poison against political opponents is a longstanding KGB trademark. Politkovskaya was unsuccessfully poisoned before she was finally shot; the anti-Kremlin Ukrainian President Viktor Yushchenko was left badly scarred after deadly dioxin was slipped into his food. And former Soviet agents speak of a clandestine secret service division, known as Laboratory 12 or "Kamera" (the Room), set up in 1920 specifically to develop poisons that will not be detected in an autopsy.
Whatever the truth, it is clear that Russian emigres in London have been spooked by the new-found assertiveness of the FSB, bolstered, they believe, by a president who no longer wishes to rein in the service's activities.
I spent two weeks shadowing the anti-Putin oligarch Boris Berezovsky and was struck by the web of security that surrounds him. He became Litvinenko's protector after Litvinenko blew the whistle on an alleged FSB plot to assassinate Berezovsky himself. In Litvinenko's case, the protection seems to have failed. Now Berezovsky must look out for himself and for the third London exile the Kremlin has named as its public enemy, Akhmad Zakayev, envoy of the pro-independence forces in Chechnya.
There is growing evidence to suggest that the FSB is again employing some of its predecessor's methods at home and abroad. It is only 15 years since the KGB changed its name, and it is perhaps sobering to remember that the operatives who were trained and promoted under the old regime are now more than likely to be in all the positions of power on Lubyanka Square.
· Martin Sixsmith's latest book, I Heard Lenin Laugh, is published by Macmillan (£12.99)