According to a new research form Google and UC Berkley, more than five million users or IP addresses are infected by adware.
According to the Verge, the number could be an underestimate since adware programs often refuse to tamper with large company sites to avoid detection.
The report also said that the infamous superfish adware, the most popular ad injector detected by the study, impacting more than 3.7 million pageviews, is still alive.
Ad-injecting malware is one of the most reliable scams on the web.
Once a computer’s infected, the virus drops new ads into any site it visits, sending ad revenue back to the scammers who control it.