Help with Threat log SCAN: Host Sweep

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Help with Threat log SCAN: Host Sweep

L1 Bithead

I am looking for assistance interpreting a report that shows “SCAN Host sweep traffic” in my threat log. There are multiple internal sources scanning multiple destination IP addresses that I do not own. The daily number of scans detected from each source is between 2 and 10. The source machine rarely scans the same destination. Is this a low level attack trying to stay under the radar or is there an explanation that does not indicate a problem on my network? I appreciate any feedback.

Type: Scan
Name: SCAN: Host Sweep
From Zone: Inside
To Zone: Outside
Source address: Internal IP address owned by me
Destination Address: various external addresses not owned by me.
Port; 99% of the time 443. Occasionally port 80 or 22222


This screen shot show traffic during one time frame. I see various Source and Destination addresses.

sample date.PNG

This screen shot is filtered by destination address. This destination address is scanned various times from different Source addresses over the course of several days.

sample destination.PNG


L1 Bithead

I see 100 views but no comments.  Is there additional information I can add to help refine my question?


Could be something attempting to beacon out. I would check the hosts for compromise and keep making sure the PAN blocks the traffic for now.

Also check the destination IP's, if they are something that your systems are supposed to be reaching out to.



Thank you for replying.  I am concerned because those addresses are not relevant to our daily business, but each machine is performing only a few sweeps a day.   I am concerned at this traffic, but wondering if I am just being paranoid?


A little paranoia is OK especially if you dont have a baseline. I would investigate the hosts and see what is actually causing the traffic.



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