To appreciate the strain online miscreants are putting on internet infrastructure, consider this: As much as three per cent of the net's traffic is malicious garbage designed to inflict damage one party or another, Arbor Networks estimates.

The endless barrage of malicious packets comprise about 1,300 distributed denial of service attacks every day, according to Arbor's ATLAS portal, which examines traffic flowing over 68 separate internet service providers. During peaks, DDoS attacks accounted for "well above" five per cent of aggregate reported traffic, according to the data, which was culled over 18 months.

By contrast, email makes up one per cent to 1.5 per cent of all internet traffic. Assuming 66 per cent of that is spam, that means about four per cent of internet packets are junk of one form or another.

Attackers mostly use DDoS attacks as a way of exacting revenge on enemies. Greg King, allegedly tried to DDoS security watchdog site CastleCops into the Stone Age after a forum participant bad-mouthed one of his reprobate friends. At its peak, the five-day attack flooded CastleCops with close to 1 gigabyte of data every second.

King has pleaded not guilty to federal charges in connection with the case.

Other targets include official Estonian websites targeted by Russian nationalists and the the Church of Scientology, which was recently taken offline by critics.

For a brief spell, attackers tried to use DDoS attacks as a means of extracting protection money from vulnerable online businesses, especially gambling sites, but that practice seems to have died down.

The most common DDoS targets observed by ATLAS were IRC servers, although the amount of junk traffic thrown at them tends to pale when compared with attacks on other targets. The most common attack vectors are SYN floods, with ICMP floods coming in a close second.

While it may seem an onerous task to generate so much junk, attackers manage to take time off during the holidays. Attack frequency drops "significantly" on Christmas Day, New Year's Eve and New Year's Day, according to Arbor's Danny McPherson, "perhaps while the miscreants are either hung over or expending their spoils." ®