The recent escalation in the conflict between Israel and Palestine has spilled over into the online world, as hacker groups have taken to defacing popular Israeli web sites.

According to reports, thousands of sites mainly belonging to small businesses have been breached.

Some very high profile sites, such as Ynetnews.com, were also hacked to display items such as a step-by-step picture guide to the progressive takeover of Palestinian land by settlers, the alleged torture of detainees by American soldiers and Palestinian victims of Israeli attacks.

Hackers also attacked the Bank Discount web site leaving anti-Israeli messages, but did not access any accounts.

"Our observations suggest that a large number of web sites have been defaced by a variety of hacker groups from Iran, Lebanon, Morocco and Turkey, and the trend is accelerating," said Bruce Jenkins, a retired major with the US Air Force, and security expert at vulnerability specialist Fortify Software.

"In the past, attacks were focused on the Department of Defense and other government organisations. But as the government, led by the US Air Force, has built up its cyber defences, hackers need to move to less suspecting targets."

Jenkins explained that the attacks are more or less random, seeking out "any company with an internet connection which has perceived or rumoured connections with the two countries involved in this conflict".

The security expert urged systems administrators at vulnerable web sites to ensure that all IT system patches are up to date, and to monitor network traffic for any unusual activity.

The battle erupted again on Saturday when Israel launched air strikes against the Gaza Strip in an attempt to bring down Hamas, which has had control of the region since June 2007 after winning the Palestinian Legislative Council elections.

Ongoing fighting has left over 600 Palestinians dead and thousands injured, with Hamas launching rocket strikes against Israel in retaliation.