Alan Ralsky, thought to be one of the world's most prolific spammers, has had his operation shut down after raids by the FBI.

Warrants unsealed last week show that the FBI raided Ralsky's home in September and seized financial records, computers and disks. The home of his son in law was also raided.

"Alan M Ralsky is notorious in the spam world, and has had a series of run-ins with the authorities over the years," said Graham Cluley, senior technology consultant at Sophos.

"Politicians who have sponsored anti-spam bills have singled him out as one of the worst offenders when it comes to junk email.

"Many will be watching closely to see if this is the beginning of the final chapter of the Ralsky story, or whether he will emerge unscathed and continue sending bulk email."

Ralsky has long been identified as one of the world's largest spammers by anti-spam organisation Spamhaus. The group describes him as a convicted felon who uses virus-infected PCs to send spam, and claims that he has hacked mail servers in the past to spread his spam. 

In 2002 Ralsky settled a case with US telco Verizon over charges that he used its network to send out large amounts of spam. 

Ralsky was also hit by a form of spam himself. A reader on technical news website Slashdot found out Ralsky's address and urged readers to send him physical junk mail, leading to van-loads of unwanted post being delivered to his home.