We can filter TCP_Port_Scan false positives by Event Filter: i.e. filter
all TCP_Port_Scan from port 80 from Internet (be sure that this traffic
is closed on firewall) or from known web sites. But ISS does not show
source port, does anybody know why?
I tried to filter all TCP_Port_Scans from 80, but seems this does not
work :-( Any ideas?
Thanks
---
Best regards, Sergey V. Soldatov.
Information security department.
-----Original Message-----
From: Jason Baeder [mailto:jason_baeder@yahoo.com]
Sent: Friday, January 13, 2006 6:59 PM
To: Soldatov, Sergey V.; issforum@iss.net
Subject: Re: [ISSForum] TCP_Port_Scan
Sergey,
I do not believe there is any effective way to tune the tcp
port scan sig in SP. Due to the limited information that SP
often provides (one my own pet peeves) it can take some work
to figure out which is a real port scan. A few pointers:
1) If you see something this "80|135|139|445|1025|2745|3127|6129"
in the port column (in Event Analysis Details view), it is
likely a port scan. I'm sure there are many theories to
explain why a series of packets will arrive at our DMZ on
those specific ports from address space at a web-hosting
company, but I think it's a port scan from an 0wn3d box.
2) If you see something like this "59097|59181|59192|59203"
in the port column, and the source IP address is one of your
public web servers, you can be sure it is HTTP return
traffic. Note the port increments....click link (HTTP GET),
scan page for desired info,click link (HTTP GET), scan page
for desired info,click link(HTTP GET)......
3) If you see something similar to #2, with a destination
address of a host inside your network (by this I mean a user
workstation), it is also likely to be mundane return traffic.
You should confirm with spot checks on source IP addresses.
You'll probably find your users are enjoying the typical mix
of Internet experiences. With HTTP you'll find similar port
patterns in the port column.
4) Finally, when in doubt, tcpdump.
This certainly doesn't cover all cases, but the most common
ones I see on a daily basis.
Regards,
Jason Baeder
--- "Soldatov, Sergey V." <SVSoldatov@tnk-bp.com> wrote:
Hi list!
In my SP console I see a lot of TCP_Port_Scan events for
Internet IPs
to my local IPs. I suppose that this are false positives
because of
HTTP replies from visited Web-sites, but unfortunately I
can't figure
out if it's so, because SP (and it's strange) does not show
attacker's
source port in event details... Does anybody can recommend
something
to help me investigate these TCP_Port_Scan events.
May be someone have experience in tuning TCP_Port_Scan event?
Any feedback will be welcome.
Thanks!
---
Best regards, Sergey V. Soldatov.
Information security department.
tel/fax +7 495 745 89 50
tel +7 495 777 77 07 (1613)
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