Snort mailing list archives
Re: sfPortscan - false positive
From: Izik Birka <Izik.Birka () hot net il>
Date: Mon, 22 Feb 2016 09:22:33 +0000
Hi What I mean is that there are servers that communicate with multiple ports like DOMAIN CONTROLLER And when hosts communicate with the DC , snort think that this is port scanning. I hope it's more make sense :) Thanks Izik Birka From: Y M [mailto:snort () outlook com] Sent: Sunday, February 21, 2016 6:36 PM To: Izik Birka <Izik.Birka () hot net il> Cc: snort-users () lists sourceforge net Subject: Re: [Snort-users] sfPortscan - false positive I am not familiar with what "EXCH" server stands for. Review what the vendor's recommendation/best practices for the network stack (protocols, ports, FW, etc) are and verify that your "EXCH" server implements the same and then only monitor these. It also depends whether you are monitoring internal vs. external network access (HOME/EXTERNAL), it really is difficult to tell with what you are describing. Give thresholds another shot and tweak, I never get them right from the first attempt [😊] . YM ________________________________ From: Izik Birka <Izik.Birka () hot net il<mailto:Izik.Birka () hot net il>> Sent: Sunday, February 21, 2016 4:18 PM To: Y M Cc: snort-users () lists sourceforge net<mailto:snort-users () lists sourceforge net> Subject: RE: [Snort-users] sfPortscan - false positive I have EXCH server , hosts are communicate with him with different ports ,because of that this is trigging alarm I can add the EXCH server ip to the ignored_scanned option , but then if someone will scan my EXCH I will not receive alarm This case is happening with many servers in my environment ... and I need to ignored them all It's pretty bummer ..... Thanks Izik Birka From: Y M [mailto:snort () outlook com] Sent: Sunday, February 21, 2016 6:09 PM To: Izik Birka <Izik.Birka () hot net il<mailto:Izik.Birka () hot net il>> Cc: snort-users () lists sourceforge net<mailto:snort-users () lists sourceforge net> Subject: RE: [Snort-users] sfPortscan - false positive In this case you need to look at your network traffic using tcpdump or something else and see what's causing the FPs. There are plenty of situations where misconfigured devices, network or otherwise, can lead to such behavior. Analyze and tweak further. I am not sure what do you mean by "not good enough". Thresholding should take care of it if configured properly. Another option is to "abuse" the reputation preprocessor and its whitelist. Though I haven't used this preprocessor for this purpose. YMMV. As for the suppression, you need to create one for each. As far as I recall, it's always been the case. Anyone, correct if I am wrong. YM _____________________________ From: Izik Birka <izik.birka () hot net il<mailto:izik.birka () hot net il>> Sent: Sunday, February 21, 2016 6:58 PM Subject: RE: [Snort-users] sfPortscan - false positive To: Y M <snort () outlook com<mailto:snort () outlook com>> Cc: <snort-users () lists sourceforge net<mailto:snort-users () lists sourceforge net>> Yes, I'm familiar with this manuals but it still not good enough , in addition I can't configure src and dst both for suppression Thanks Izik Birka From: Y M [mailto:snort () outlook com] Sent: Sunday, February 21, 2016 5:43 PM To: Izik Birka <Izik.Birka () hot net il<mailto:Izik.Birka () hot net il>> Cc: snort-users () lists sourceforge net<mailto:snort-users () lists sourceforge net> Subject: Re: [Snort-users] sfPortscan - false positive For thresholding, check this: http://manual.snort.org/node35.html For suppression check this: http://manual.snort.org/node207.html As you will note, these do not operate at the port level, its a combination of sid / gid / src or dst IP. YM ________________________________ From: Izik Birka <Izik.Birka () hot net il<mailto:Izik.Birka () hot net il>> Sent: Sunday, February 21, 2016 3:35 PM To: Y M Cc: snort-users () lists sourceforge net<mailto:snort-users () lists sourceforge net> Subject: RE: [Snort-users] sfPortscan - false positive This is my configuration # Portscan detection. For more information, see README.sfportscan preprocessor sfportscan: proto { all } \ memcap { 10000000<tel:10000000> } \ sense_level { low } \ ignore_scanners { IP,IP,IP } \ ignore_scanned { IP,IP/24,IP,IP/24, IP,IP,IP } \ scan_type { portscan } as you can see I configured scan_type and I start to Exclude IPs than I realize that it's going to be a hard work so I stast searching for better solution , what can I configured in the thresholding file ? I want for example to receive alert for 10 ports attempted scanned or more per ip - this will reduce a lot of my alerts... From: Y M [mailto:snort () outlook com] Sent: Sunday, February 21, 2016 4:33 PM To: Izik Birka <Izik.Birka () hot net il<mailto:Izik.Birka () hot net il>> Cc: snort-users () lists sourceforge net<mailto:snort-users () lists sourceforge net> Subject: RE: [Snort-users] sfPortscan - false positive If you review the sfportscan configurations here: http://manual.snort.org/node79.html, you can specify the scan type and the scan sensitivity, watch, and ignore. Portsweep is different than port scan, is just an example. sfPortscan Configuration - SNORT Users Manual 2.9.7<http://manual.snort.org/node79.html> manual.snort.org<http://manual.snort.org> Format Up: sfPortscan Previous: sfPortscan Contents sfPortscan Configuration. Use of the Stream5 preprocessor is required for sfPortscan. Stream gives portscan ... YM Sent from Mobile On Sun, Feb 21, 2016 at 6:28 AM -0800, "Izik Birka" <Izik.Birka () hot net il<mailto:Izik.Birka () hot net il>> wrote: How this data can help me ? if I can't change the ratio I continue to get false positive alerts Is there any way to configure the number of scanning attempt and the time period for alert to show ? In the past the command was bit different and I was able to configure it Example : Preprocessor portscan: 192.168.1.0/24 10 60 10 is the number of scanning attempt 60 is time period Thanks Izik Birka From: Y M [mailto:snort () outlook com] Sent: Sunday, February 21, 2016 4:20 PM To: Izik Birka <Izik.Birka () hot net il<mailto:Izik.Birka () hot net il>> Cc: snort-users () lists sourceforge net<mailto:snort-users () lists sourceforge net> Subject: Re: [Snort-users] sfPortscan - false positive I believe they refer to the data generated by the preprocessor. Review the distribution of the data points mentioned. I am not on a computer to verify. YM Sent from Mobile On Sun, Feb 21, 2016 at 3:20 AM -0800, "Izik Birka" <Izik.Birka () hot net il<mailto:Izik.Birka () hot net il>> wrote: Hi I'm trying to tune PortScan false Positive I found this explanation in snort site Make use of the Priority Count, Connection Count, IP Count, Port Count, IP range, and Port range to determine false positives. But I didn't understand where I can change those values , Who knows ? Thanks Izik Birka This message (including any attachments) is intended only for the use of the individual or entity to which it is addressed and may contain materials protected by copyright or information that is non-public, proprietary, privileged, confidential, and exempt from disclosure under applicable law or agreement. If you are not the intended recipient, you are hereby notified that any use, dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication by error, notify the sender immediately and delete this message immediately. Thank you. This message (including any attachments) is intended only for the use of the individual or entity to which it is addressed and may contain materials protected by copyright or information that is non-public, proprietary, privileged, confidential, and exempt from disclosure under applicable law or agreement. If you are not the intended recipient, you are hereby notified that any use, dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication by error, notify the sender immediately and delete this message immediately. Thank you. This message (including any attachments) is intended only for the use of the individual or entity to which it is addressed and may contain materials protected by copyright or information that is non-public, proprietary, privileged, confidential, and exempt from disclosure under applicable law or agreement. If you are not the intended recipient, you are hereby notified that any use, dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication by error, notify the sender immediately and delete this message immediately. Thank you. This message (including any attachments) is intended only for the use of the individual or entity to which it is addressed and may contain materials protected by copyright or information that is non-public, proprietary, privileged, confidential, and exempt from disclosure under applicable law or agreement. If you are not the intended recipient, you are hereby notified that any use, dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication by error, notify the sender immediately and delete this message immediately. Thank you. This message (including any attachments) is intended only for the use of the individual or entity to which it is addressed and may contain materials protected by copyright or information that is non-public, proprietary, privileged, confidential, and exempt from disclosure under applicable law or agreement. If you are not the intended recipient, you are hereby notified that any use, dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication by error, notify the sender immediately and delete this message immediately. Thank you. This message (including any attachments) is intended only for the use of the individual or entity to which it is addressed and may contain materials protected by copyright or information that is non-public, proprietary, privileged, confidential, and exempt from disclosure under applicable law or agreement. If you are not the intended recipient, you are hereby notified that any use, dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication by error, notify the sender immediately and delete this message immediately. Thank you.
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Current thread:
- Re: sfPortscan - false positive, (continued)
- Re: sfPortscan - false positive Izik Birka (Feb 21)
- Re: sfPortscan - false positive Y M (Feb 21)
- Re: sfPortscan - false positive Izik Birka (Feb 21)
- Re: sfPortscan - false positive Y M (Feb 21)
- Re: sfPortscan - false positive Izik Birka (Feb 21)
- Re: sfPortscan - false positive Y M (Feb 21)
- Re: sfPortscan - false positive Izik Birka (Feb 21)
- Re: sfPortscan - false positive Y M (Feb 21)
- Re: sfPortscan - false positive Izik Birka (Feb 21)
- Re: sfPortscan - false positive Y M (Feb 21)
- Re: sfPortscan - false positive Izik Birka (Feb 22)