Blue Security started its Blue Frog anti-spam initiative last year, with members reporting every single piece of junk mail to the website, which then sent requests for those names to be removed from mailing lists.

This meant spammers' websites were receiving thousands of clean-up requests every day - which left them a bit miffed.

In retaliation, the junk mailers started targeting Blue Security's website by sending vast amounts of data, which the site's server couldn't handle. A number of Blue Frog members also received threatening e-mails.

The company now says it's ending the scheme, because it "cannot take the responsibility for an ever-escalating cyber war through our continued operations", the BBC reported.