Just curious: is anyone else seeing a large amount of Invalid SACK block alerts after updating to the latest signature set?Correction- this seems to be related to the updated sensor software that I installed around the same time as the signature set update.
Yes, we are seeing more of these among mail servers for different organizations. They can happen in clusters of a few over several minutes and you can watch the dissemination among servers, or they can happen singly. I cannot find any direct malicious intent, the servers are not impacted, destination ports are 25, 80, 443, 5600 and 5601. the outside sources all seem legit so far. With just the sensor data to work with, given the number of diverse sources and the, thus far, benign impact I could say we have a lot of false positives.