A bug, which appeared in an antispam rule update, began blocking and quarantining all incoming and outgoing messages containing the letter "P," depending on how customers had configured the software. The flaw affected a Trend Micro product designed to filter content, block unsolicited commercial e-mail, and report and monitor the type of information that enters or leaves a company's network.

The problem affected Cupertino, Calif.-based Trend Micro's eManager product, an e-mail security product. A company representative said the number of customers who reported being affected was in the low double digits.

The problem occurred in rule No. 915, which updates antispam parameters. The security firm quickly released a fix with rule No. 916 and posted it to its site Tuesday. Rule No. 915 was available for only an hour and a half before Trend Micro issued rule No. 916.

[ Read more ]