The CBL issued a statement and explanation for the false positives. Copying it here because there doesn’t seem to be a way to link directly to the statement on the CBL front page.
November 24, 2015Â Widespread false positives
Earlier today, a very large scale Kelihos botnet event occured – by large scale, many email installations will be seeing in excess of 20% kelihos spam, and some will see their inbound email volume jump by a volume of as much as 500%. This isn’t an unusual thing normally, the CBL/XBL has been successfully dealing with large scale Kelihos spam spikes like this, often daily, for years.
The email was allegedly from the US Federal Reserve, saying something about restrictions in “U.S. Federal Wire and ACH online payments.” Not only was the notice itself fraudulent, the attached Excel spreadsheet (.xls) contained macro instructions (a downloader) to download a Windows executable virus, most likely Dyreza or Dridex malware.
The detection rules initially deployed by the CBL unfortunately were insufficiently detailed, and listed a number of IP addresses in error.
As per our policy, all entries of this type were purged (by about 19:05 UTC), and the detection heuristic removed.
If you were listed up to around 19:00 UTC, and the CBL lookup page appears to indicate that the IP is no longer listed, this is likely the explanation, and no further action is required on your part.
Out of curiosity I checked my own mailboxes. Since the first “Federal Reserve Spam” delivered at around 3:45 this morning, I’ve received 252 spams. 124 of those were the Kelihos bot spam. So it’s a good half of today’s spam volume. Yesterday’s total spam volume was around 328. A noticeable increase here.
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Any chance that a similar situation is happening now?