Poople who use a popular programme to chat on the internet have been advised to download a software upgrade following the discovery of a potential security breach by a software engineer based in Ennis, Co Clare.

Mr James Martin, a freelance computer programmer, told The Irish Times yesterday he had uncovered a security weakness with mIRC, a type of internet relay chat software used by millions of computer users.

The "security hole" could be exploited by rogue users to take control of a user's computer because of an error in the way the software handles messages from internet servers, said Mr Martin.

Mr Martin informed the developers of mIRC about the security breach last year but did not publicise the problem until an upgrade was released this week and could be downloaded by users.

"I was just messing around [with mIRC\] and noticed something weird was happening but then noticed it was much more serious than that," he said.

Mr Martin was given the Beta version of the upgrade programme to test last week and it was finally released on Sunday. The upgrade programme, version 6.0, can be downloaded at www.mirc.com.

The developers behind mIRC software told the BBC this week that they had been planning to release an upgrade of the software, but described Mr Martin's help as "invaluable".

"Hopefully, the exploit has been solved in the new version, although these days it's hard to know since so many people are constantly looking for ways to exploit issues like this," the developer of mIRC, Mr Khaled Mardam-Bey, said.

Mr Martin is also involved in a project to build a nationwide wireless local area network throughout Ireland to circumvent the current difficulties in obtaining broadband internet access.

His personal website address is www.uuuppz.com.