Rik Ferguson, director of Trend Micro's European security research efforts, said the file was "a functional OS with a bunch of pre-installed tools that can be used for things like looking for database vulnerabilities or password cracking". It also included tools such as Tor that can mask a person's online activities.
Graham Cluley, senior researcher at security firm Sophos, wondered who would be tempted to use it.
"Who would want to put their trust in a piece of unknown software written by unknown people on a webpage that they don't know is safe or not?" he asked in a blog post.
He warned people to be very wary, adding that some hacktivists keen to support the work of Anonymous had been tricked earlier in the year into installing a booby-trapped attack tool.
Sophos hasn't analysed the Anonymous OS download yet.
"Anonymous OS isn't a threat to the average guy in the street or to office workers, the only people who might be impacted by it are those who are foolish enough to knowingly install unknown software onto their computers," Cluley commented.