@andrew75 @flood Mysteriously, the symptoms have gone away, which makes it impossible to find out what has been happening, but they went away at different times on different PCs, which make me wonder whether they are related to updates of KIS at different times on different machines. The specifics are: On PC-C (my machine) the blocks came from startup today (1/7) at 9:11 about every 2 mins (but not consistently so) until I turned off Network Attack Blocker at 13:15. The last NAB event was 13:07 and there are no events of any type between the two. I put in @andrew75’s suggested rule and restarted NAB at 15:47, since when there have been no block events. Given the experience on the other two machines, that may have been a coincidence. On PC-A, the first block was at 10:06, probably when the PC was switched on, recommenced at 11:06 (presumably the 60 min grace period in KIS’s standard settings) and continued every 2 mins until 13:05. No apparent reason for the change at 13:05. On PC-J, the blocks started at 20:46 on 30/6 and continued until 20:53. None since. I will pass these notes to Kaspersky Support, who have responded to my report of a False Positive, but there does not seem to be any point in putting in any more work on the issue unless the symptoms reappear. Many thanks both of you for your help.