Yahoo Messenger users who had the misfortune to follow the link in an advert for Vietnamese Internet directory website LaBan.vn and download the offered executable have been saddled with a persistent app that repeatedly leads them to the website.

"It is not yet clear whether the banner has reached YIM customers following a legit advertising campaign that was modified by the advertiser later, or if it is an abusive attack that exploits a bug in the Yahoo Ad services," says Bitdefender's Bogdan Botezatu, but the banner was displayed for four hours.


The problem with the app is that it can't be easily deleted. The app adds itself to the Windows startup entries in order to get run after every system reboot, and it repeatedly changes the default start page of the browsers found on the affected computer.

The researcher doesn't mention whether the LaBan.vn website offers other malicious software except for this app, but even if it doesn't, it must get pretty annoying being taken to a page you don't want to visit every time you open a browser - and not to mention probably very lucrative for the site's owners.

For those unlucky users who have already installed the app, Bitdefender offers a free removal tool for both 32- and 64-bit operating systems.

It goes without saying that users should avoid installing unknown files that get offered by random sites.