In a glaring contrast to Symantec's Wednesday post that the number of Flashback-compromised Mac computers had dropped from around 600,000 to nearly 140,000, Russian antivirus firm Dr. Web said on Friday that, going by the latest estimates, Flashback malware was still affecting approximately 650,000 unique OS X systems.
Going by the details shared in Dr. Web's most recent post, an estimated total number of 817,879 bots have seemingly been a part of the Flashback botnet at one time or another since the firm first began monitoring it on April 4.
Furthermore, the number of unique IP addresses and Mac unique user IDs which checked in on Monday stood at 717,004 and 595,816 respectively; with the check-in figures for Tuesday being 714,483 and 582,405 respectively. As such, as per Dr. Web, the estimated number of Flashback-infected Macs was "still around 650,000."
With Dr Web elaborating that the revised numbers of Flashback-infected Macs were an upshot of the so-called `sinkholes' which are constructed by researchers to act as surrogate command and control servers for the hacked computers, Symantec soon updated its post to add that its researchers believe that their servers were now receiving "limited infection counts" for Flashback.
Meanwhile, noting that a significant number of Macs were still infected, though they cannot be counted by sinkholes, Peter James - a researcher at Mac antivirus provider Intego - said: "The realization now that the actual number of infected Macs is a multiple of the numbers cited recently in the press suggest that as many Macs are disinfected others are being infected."