Hanssen reportedly suspected he was under surveillance by the FBI, telling his Russian contacts, "something has aroused the Sleeping Tiger," said the FBI in an affidavit released March 1, 2001.

The comment came from a letter FBI officials say was encrypted on a diskette found in a package that Hanssen dropped in Northern Virginia immediately before his arrest.

In his house authorities found an AK-47, 13 other guns, phony identification documents, including passports, international bank account documents and jewellery, which the affidavit said were "the proceeds of assets derived from illegal espionage transactions."

"Dear Friends," the letter reads, according to the affidavit, "I thank you for your assistance these many years. It seems, however, that my greatest utility to you has come to an end...Since communicating last, and one wonders if because of it, I have been promoted to a higher do-nothing senior executive job outside of regular access to information within the counter-intellegence program. It is as if I am being isolated. Furthermore, I believe I have detected repeated bursting radio signal emanations from my vehicle... Something has aroused the sleeping tiger. Perhaps you know better than I."

Facts and affidavit quotes taken from cnn.com.