IT managers are bracing themselves for a flood of web defacement attacks this weekend as vandals take part in this year's run of The Defacers' Challenge.

The annual hacking competition involves players scoring points for defacing up to 6,000 websites, or inserting their own pages, in the shortest possible time.

This year's event starts on Sunday 6 July and security professionals are already seeing increased hacking activity in the run up.

"There has been a big rise in precursory, reconnaissance-style scanning," said Gunter Ollman, head of Internet Security Systems' X-Force in Europe.

"People - I'd hesitate to call them bona fide hackers - are stockpiling vulnerable sites so they can get large point scores fast.

"There's also been a distinct lack of defacements recently; it seems these people are holding back on their usual activities unless they get some kind of score for it."

Different web servers are scored according to operating system: Windows (one point), Linux, Unix and BSD (two points), AIX (three points), HP-Unix and Mac (five points).

The most likely method of defacement will probably come from malware implanted on web servers before the competition starts.

"Get patching now," warned Neil Barrett, technical director at security consultants IRM.

"There'll be a series of hacking tools deployed against your servers as you're reading this, and come Sunday they'll be deployed to maximum effect."