Some nasty ads have hit the Web browsers of visitors to NYTimes.com and some other sites in recent days. The ads, which are not authorized or endorsed by The Times, can hijack a person’s browser and make it appear as if a scan for viruses is running. The ads then promote “antivirus” software that is itself virus-like. The Times believes it has eliminated these ads, but if they popped up on your screen, here’s what you need to know about your computer’s security.
According to Rik Ferguson of the security-software maker Trend Micro, a malicious ad sparked a pop-up window with a bogus claim that the PC was infected with malware. It urged the user to run a system scan with its “Personal Antivirus” program — a convincing-looking ruse, but a complete fake — to clean out the infection.