Updated Users of the ad-supported version of Spotify were hit by a malware-based attack on Thursday.
The assault takes advantage of a Java-based exploit to deposit Trojan horse malware or exploit kits on vulnerable Windows machines. Only users of the free version of the music streaming service seem to be affected.
In response, Spotify pulled its ad feed on Friday while it investigating the problem.
We're currently investigating and have pulled all third party display ads that could have caused the problem until we locate the specific advert.
El Reg became aware of the problem on Thursday, following a tip-off from a reader in UK academia. JANET (Joint Academic Network) is reportedly looking into incidents of viral warnings linked to Spotify. "We're not investigating any specific infections at this moment, but our community is asking for more info," it said.
The malware was served up via malicious third-party adverts, a factor that means the threat is not persistent and may be region specific. This makes it harder for anti-virus firms to pin down the outbreak.
But the problems was far from isolated, with several Twitter users reporting the same issue over the last day or so. Both Avast and AVG are detecting the exploit.
Netcraft has a precis of the attack, which is still under investigation, here. ®