Sophos' senior technology consultant Graham Cluley, said in a blog post Thursday, the antivirus company found 11 percent of users who had taken an endpoint assessment test at its Web site did not have the Microsoft OS08-067 patch installed.
The patch, available since October last year, fixes a vulnerability which allows the Conficker worm to infect PCs.
The Conficker saga has been broiling for the last month or so, where it received a swarm of media attention leading up to April 1--when it was expected to detonate. Its real effects were seen about a week later, when it started dropping a mystery payload on infected computers.
Microsoft has also put up a US$250,000 reward for information leading to the arrest and conviction of the criminals behind the worm.
Cluley said in his blog post the 11 percent of infected PCs is "pretty depressing news", given the press coverage the worm has received.
"It appears that the percentage of computers not patched against the exploit is holding steady," he added.
The goal of Conficker's creators remains unclear. While researchers have said the worm's payload dumping activity indicates a profit motive, such as stealing passwords or spam-generation, Conficker has yet to fully reveal its intended function.
There are a number of tests and checks online, including an eye chart from the endpoint assessment test for the Microsoft patch.
Sophos is offering a tool to remove the Conficker worm from infected PCs, as well.
This article was originally published on ZDNet Asia.