A drive to stop spammers targetting particular email addresses misfired earlier this week, after a spammer began to send large quantities of unsolicited email to members of a "Do Not Spam" list run by Blue Security.

In recent days, email users who had registered for Israeli firm Blue Security's "Do Not Intrude" list have instead been the target of a spam campaign and received extortion email messages threatening to continue the campaigns unless the users remove their name from the Do Not Intrude registry, according to Blue Security CEO Eran Reshef.

The message claims that Blue Security is "not playing fair" and that members can avoid spam messages only by removing their name from the Blue Security list.

"You are receiving this email because you are a member of Blue Security," the message reads, in part. "Due to the tactics used by Blue Security, you will end up receiving this message, or other nonsensical spams 20–40 times more than you would normally."

Blue Security launched its "Do Not Intrude" list in November 2005. The company claims to have 500,000 registered email addresses in its database, plus business relationships with other antispam firms.

The Do Not Intrude program allows individuals to register an email address with Blue Security and tracks spam messages with desktop-client software known as Blue Frog. When spam email is sent to a Do Not Intrude Member, Blue Security traces the message to its origin and then bombards the website behind the campaign, known as the sponsor, with requests to remove the email message from his or her distribution lists. Millions of email messages translate into millions of "opt out" requests, bogging down the spammers' servers.

The spam campaign is a sign of Blue Security's success and an act of frustration by a major spammer based in Russia, Reshef said.

"It's one of the top spammers. We're not sure which one at this point, but six of the top 10 are complying with [Blue Security], so it's one of the remaining four," Reshef said.

Blue Security's growth in recent months has forced major spam operations in Russia to stop sending to Blue Security members, Reshef claims. Those Russian spammers account for around 25 percent of the 4.5 million emails Blue Security receives each week.