Irish companies should prepare for a rapid increase in the kind of cyber attacks which brought down social networking site Twitter last week, according to a leading IT expert.

Twitter was brought down for two hours last week by a distributed denial of service attack which saw computers bombard the social networking website with requests for information blocking off legitimate users in the process. A similar attack brought down Eircom's broadband service for five hours two weeks ago.

Irish businesses should consider expanding their own bandwidth if they want to avoid falling prey to sophisticated criminals, according to Andy Harbison, director of Grant Thornton's Forensic & Investigation Services.

"I would be worried if my business was heavily dependent on the web as a marketing vector and I did not have a lot of capacity. I would be talking to my Internet Service Provider (ISP) about capacity and how I would get out of that situation ... I have no doubt this will happen more often," he said.

Businesses who do not host their website with an ISP are particularly vulnerable because of diminished capacity. While the Twitter attack appears to be politically motivated, denial of service attacks are normally the preserve of organised criminal gangs who want to commit fraud.