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SG310 UTM - SID 20842 - Suddenly getting regular intrusion prevention alerts from various source IPs to Windows 10 hosts

First alert we had from rule SID 20842 was on 23 Nov at 17:39 GMT. Since then have had 230 alerts to around 50 different Windows 10 hosts, all this rule, 29 different IP source addresses, all source port 80, various destination ports.

Looking up the source IP addresses most of them look like CDN IPs, some identified as Akamai Technologies, couple I've seen Microsoft update mentioned. Looking at netstat on one host it looked like SearchApp.exe was connected to one of these sources. I checked the SearchApp.exe program certificate and it was genuine.

I just can't understand why this rule is suddenly generating these alerts. If the IPs are genuine CDN sources, why they are generating alerts? I'm not aware of any network or firewall changes that could be a factor.

I've logged a ticket with support, but haven't heard anything back and am desperate to understand what is going on here.

  • Are these false positives or do we have malware on the network?
  • If they are false positives why can't I find anything about this particular rule?
  • Do people routinely disable IPS rules that generate false positives, or whitelist lots of domains after checking they are legit?

Top 10 IPS sources since first alert (all rule 20842):

1
23.73.136.145
66
2
23.73.136.89
52
3
13.107.4.50
28
4
178.79.251.0
12
5
8.238.11.126
7
6
2.22.146.145
6
7
8.238.5.126
5
8
8.238.3.254
5
9
2.22.146.144
4
10
8.238.55.126
4

Full email alert:

Intrusion Prevention Alert

An intrusion has been detected. The packet has been dropped automatically.
You can toggle this rule between "drop" and "alert only" in WebAdmin.

Details about the intrusion alert:

Message........: FILE-OTHER Interactive Data eSignal stack buffer overflow attempt
Details........: https://www.snort.org/search?query=20842
Time...........: 2021-11-23 17:39:17
Packet dropped.: yes
Priority.......: high
Classification.: Attempted User Privilege Gain
IP protocol....: 6 (TCP)

Source IP address: 13.107.4.50
Source port: 80 (http)
Destination IP address: 192.168.[x].[x]
Destination port: 58759

---

  • Model: SG310
  • Firmware: 9.707-5
  • Pattern: 205149

Any help would be very much appreciated.



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  • Hi,

    Just created a case for the same issue.

    2021:11:29-12:13:15 fw snort[26400]: id="2101" severity="warn" sys="SecureNet" sub="ips" name="Intrusion protection alert" action="drop" reason="FILE-OTHER Interactive Data eSignal stack buffer overflow attempt" group="500" srcip="8.238.111.126" dstip="172.16.x.y" proto="6" srcport="80" dstport="50273" sid="20842" class="Attempted User Privilege Gain" priority="1" generator="1" msgid="0"

    2021:11:29-12:13:15 fw snort[26400]: id="2101" severity="warn" sys="SecureNet" sub="ips" name="Intrusion protection alert" action="drop" reason="FILE-OTHER Interactive Data eSignal stack buffer overflow attempt" group="500" srcip="8.238.111.126" dstip="172.16.x.y" proto="6" srcport="80" dstport="50273" sid="20842" class="Attempted User Privilege Gain" priority="1" generator="1" msgid="0"

  • Thanks Stefan. I logged my case with support on the 24th and apart from asking my availability for a remote session it's gotten nowhere yet. Hope you have more luck...

  • I got this answer at my case:

    "Has Rule ID 20842 been added to Network Protection > Intrusion Prevention > Advanced > Manual Rule Modification > Rule ID = 20842 and set the action to drop? If not, can this be done, please?"

    This seems to work, but I am not an expert in firewall's and not sure if this lowers the security. I asked this, but did not get an answer yet.

  • Thank you for telling us  this first workaround!

  • The automatic rule allready drops the packets matched by the rule

     severity="warn" sys="SecureNet" sub="ips" name="Intrusion protection alert"  action="drop"  reason="FILE-OTHER Interactive Data eSignal stack buffer overflow attempt" group="500" srcip="8.238.151.254" dstip="192.168.xxx.yyy" proto="6" srcport="80" dstport="54442" sid="20842" class="Attempted User Privilege Gain" priority="1" generator="1" msgid="0"  

  • yes right, then we have won nothing

  • Exactly, I know the IPS alerts are already being blocked and can be silenced manually, but I don't want to without knowing what's changed, what's causing them. I've never had to do this before. When you search for the 20842 rule ID and message, this post comes up but there's a lack of other reports from other systems, which surely there would be if it was a problem with the Snort database.

    Has anyone had any luck packet tracing on affected hosts?

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  • Exactly, I know the IPS alerts are already being blocked and can be silenced manually, but I don't want to without knowing what's changed, what's causing them. I've never had to do this before. When you search for the 20842 rule ID and message, this post comes up but there's a lack of other reports from other systems, which surely there would be if it was a problem with the Snort database.

    Has anyone had any luck packet tracing on affected hosts?

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