The Japan-based antivirus company has promised to compensate customers whose computers running Windows XPwere disabled by the update. The company said the update was only available for 90 minutes, but IT workers are angry.
"This...update took down virtually all 1,500 of our Windows XP SP2 PCs and required many hours of work to resolve," said one angry person in an e-mail sent to ZDNet UK. "The machines were rendered inoperable once this signature hit and required many of us to work through Friday night. Our entire IT staff had to come in on Saturday to attempt to fix this disaster."
"How in the world could Trend (Micro) release a signature file that disables all Windows XP SP2 machines? Why didn't (they) test this signature before it got released?" the person added.
Another person reported that every one of his company's 250 desktops had to be visited by a technician and repaired after being hit by the problem.
Trend Micro, which denied rumors that the update included a virus,.
The company said that it didn't know what had caused the latest incident but that it had now issued a fix and was working with channel partners to solve the problem.
"We apologize to the people, and we are willing to compensate them for the extra work they had to do (on) their machines," said Raimund Genes, president of Trend Micro for Europe. "It's a pattern file that we made a mistake on. I would say this is an isolated incident, but we have to figure out why it wasn't caught by the quality assurance."
A Trend Micro spokeswoman later said that compensation claims would be assessed "on a case-by-case basis."
Genes said that most of the businesses affected were located in Japan, and that few complaints had been received from customers in the United States and Europe.
Investors of the company have been informed, but Genes said the incident could affect share prices. Analysts said that while the immediate financial impact may be small, the long-term effects could be more serious.
"The total cost related to this matter is not likely be huge, but what investors want to see is whether the company can maintain its brand name as a leading antivirus maker," said Yoshihiko Kosuga, equities deputy general manager at Mizuho Investors Securities. "These kind of incidents do hurt the corporate image and name."
The update affected versions 7.5 and above of Trend Micro's Scan Engine.
Dan Ilett of ZDNet UK reported from London. Reuters contributed to this report.