Anonymous members have taken responsibility for launching a denial of service attack against Wikileaks this week using a custom-built tool that exploits a SQL server flaw.

Members were conducting field tests of the tool dubbed RefRef against several websites including WikiLeaks, Pastebin and was hitting 4Chan at the time of writing.

Users of a Twitter account linked to the RefRef attacks and an AnonOps blog described themselves as hacktivist with “a personal vendetta against WikiLeaks” adding that “we are sorry we took you down. We are even.”

Other Anonymous users had pledged support for Wikileaks and during this year and 2010 launched attacks against organisations which hindered or reviled the whistleblower organisation.

The RefRef tool was under development for months and was due for release mid September.

It exploited a known SQL injection vulnerability that overwhelmed a target’s resources by "using a target site's own processing power against itself" according to an AnonOps blog.

The tool would become useless against websites that had patched the vulnerability.

“So far, what they have is something that is platform neutral, leveraging JavaScript and vulnerabilities within SQL to create a devastating impact on the targeted website,” the AnonOps blog said.

“Previously, Low Orbit Ion Canon (LOIC) was the go to weapon for Anonymous supporters during protests against dictators in North Africa, and Operation: Payback. However, LOIC is also the reason scores of people have been arrested in the last year, so many feel its time is at an end.

“An attack vector that has existed for some time, resource exhaustion is often skipped over by attackers who favour the brute force of a (Distributed Denial of Service) attack sourced from bots or tools such as LOIC”.

Pastebin administrators in a tweet asked Anonymous to not “test your software on us again”.

More to follow.