As expected, spam levels are heading back up after dropping dramatically following the shutdown of McColo. According to MessageLabs, now part of Symantec, spam levels decreased by about 80% when the spammer’s hosting firm was disconnected recently, but the remaining 20% has almost doubled to 37% since last week.

Computers that are part of the Srizbi botnet – which by some estimates send nearly half of the world's spam – are apparently becoming active again, with the lag between the initial decline and the subsequent rise being attributed to the time it took for the spammers to find a new ISP and bandwidth provider.

The resurgence of spam is not at all surprising but it is disappointing to hear that, two weeks after the McColo shutdown, no federal agency has been able to seize the servers used to control these operations, which of course conceal a potential treasure trove of evidence against the cybercriminals.