Controversial Israeli security company Blue Security has been under siege from spammers for the past few days. 

The company's business websites had been under a sizeable denial of service attack for a number of days, it emerged over the weekend. The most likely attackers are spammers angered at the firm's aggressive tactics.

Blue Security has been offering a tool for download to members of its 'Do Not Intrude' registry since last year.

The Blue Frog tool traces and floods senders of unwanted email with opt-out mails, a technique that has been likened to spamming itself. 

But members of the registry received threatening emails from the spamming community last week, warning them to quit the service.

A large-scale distributed DoS attack was underway shortly after. At some points, Blue Security reckons it was being flooded by around 10 million packets a second.

Guy Rosen at Blue Security emailed the Sans Internet Storm Centre giving a breakdown of the week's activities.

"Monday: Spam-based threats and accusations; Tuesday: Our website is cut off from outside Israel by a mysterious routing change; Later on, huge DDoS lashes out at our servers; DDoS continues as we relocate our service to bring it back up. One estimate was of something of the order of 10 million packets/sec coming in," he wrote.

However, at one point it emerged that Blue Security had drawn yet more concern from other areas of the industry by seeking to dodge the DDoS attack.

The company reinstated an old blog and then rerouted its DNS to the blog address. The weight of the attack apparently brought down the entire blogging services of TypePad and LiveJournal.