The problematic pattern file was posted Friday afternoon and taken down an hour and a half later. Customers using Trend Micro's OfficeScan, PC-cillin, and three other products on systems running Windows XP Service Pack 2 were affected.
The flawed update caused high CPU utilization, causing system instabilities, said Michael Sweeny, Trend Micro spokesman. The company received some reports of systems locking up. Sweeny said customers around the world were affected but that it was difficult to estimate the number.
"We are deeply concerned and we sincerely apologize," he said.
Trend Micro has been reaching out to customers and its channel partners about the problem, and extended its support hours to help customers, Sweeny said.
The company is reviewing its product development and quality assurance processes to ensure balance "between timely updates and delivering the quality our customers need," he said.
Pattern file 2.594.00 aimed to protect customers against the RBOT family of malware with new heuristic techniques, including "UltraProtect decompression."
"Due to an isolated anomaly in the engineering, development and pattern release process, the UltraProtect decompression may, in certain circumstances, cause some systems to experience high CPU power consumption," Trend Micro said in a statement.
The SANS Internet Storm Center received reports about the problem from its readers.
"Several readers wrote in to say that they were clueless about the 'sudden dead' of their systems. It took them several hours and pain to diagnose the problem...," incident handlers at the ISC said.
Trend Micro posted an advisory about the problem on its web site, www.trendmicro.com.