A leading technology firm has raised its alert level to high in relation to the Internet virus MyDoom.
Computer Associates International said it has raised the "threat level" based on "extremely intensive activity levels and exponential growth".
The virus has hit the world's most popular search engine, Google, and other market leaders.
"Computer users are cautioned to verify any unsolicited emails with senders," the software company, which has an operation in Dublin, said.
MyDoom caused "slowness" for a short period yesterday on Google and other leading search engines including Lycos and Altavista. It also affected e-mails.
In a statement, Google said yesterday: "The Google search engine experienced slowness for a short period of time earlier today because of the MyDoom virus, which flooded major search engines with automated searches.
"At no point was the Google website significantly impaired, and service for all users is expected to be restored shortly."
Computer Associates urged users to beware e-mails containing subject lines such as hello, hi, error, status, test, report, delivery failed, Message could not be delivered, Mail System Error - Returned Mail, Delivery reports about your e-mail, Returned mail: see transcript for details, and Returned mail: Data format error.
Additional reporting PA