Questions tagged [snort]

Snort is an open source network intrusion detection and prevention system (NIDS/NIPS).

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Snort DNS rule immersive labs [closed]

The question is "Create a rule to detect DNS requests to 'interbanx', then test the rule with the scanner and submit the token." My rule is: alert udp any any -> any 53 (msg:"alert&...
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51 views

SNORT rule for detecting/preventing unauthorized VPN or encrypted traffic

Here's my not so theoretical scenario: A day-one Trojan horse attack where the attacker sets up a secure connection back to himself using a well known trusted port, such as 80 21 443. Or for instance, ...
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Can I use Snort to detect multiple VLANs over site to site VPN?

I am studying options to check traffic over multiple VLANs using a Snort cloud machine, since the normal Snort installation requires to get local network and local VLAN information. I thought to use ...
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60 views

Blocking FTP Brute Force Attack with Snort

I am trying to become familiar with Snort, and for this reason, I have set three VMs. A Kali, a windows machine with XAMPP and Ubuntu where I installed Snort. I believe I have Snort running in ...
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Snort can't detect ARP spoofing?

I am learning about Snort and ran into a problem that i don't really understand. My virtualized test lab consists of: a pfSense VM with Snort (192.168.1.1), an Ubuntu VM (192.168.1.100, 00:0c:29:da:...
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Snort Alert doesn't filter source port 80

My problem is as followed: I have a pcapng file with around 125k packets. 57k packets are from destination port 80 to a range of port 20943 to 24519. Below is my very simple alert, which for now does ...
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46 views

Snort doesn't capture raw packets

I have a python code on Linux to create a raw packet: import socket s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_TCP) s.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1) ...
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87 views

Snort Inline Mode(IPS) Routing Packet Forwarding

I'd like to build an IPS which would be a seperate endpoint than the router and/or protected servers. To achieve this I've installed to my Ubuntu server Snort with DAQ(AFPACKET). The instructions I've ...
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33 views

need help using PCRE in snort

Can someone guide me how to write PCRE option to match list of websites such as for eg facebook.com, google.com,ebay.com? I tried to understand from manual but couldn't get is right? regards,
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39 views

using dsize:<500 parameter in snort

I am tring to make rule to alert when downloading jpg file less than certain size . i used parameter dsize:<500; But it is not alerting when i tried to run pcap file containing jpg less than 500MB. ...
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Snort automatic protocol detection

Does Snort have the "automatic protocol detection" function like Suricata? I read that Snort 3 has "Autodetect services for portless configuration" feature. Does it mean that this ...
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1k views

Difference between Zeek (Bro) and Snort 3

I'm trying to find difference between Zeek and Snort 3. Сan anybody tell me what are the advantages of Zeek against Snort 3?
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Snort analyze reply based on request

I'm trying to write a snort rule which detects if certain binary files where requested via HTTP based on a regex rule matching there names. But it should only send an alert if the file exists (e.g. ...
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80 views

ids - How do I match any string in a list of snort contents?

If I do something like alert tcp any any <> any any (content:"TestA"; content:"TestB"; sid:1000000; msg:"Syntax correct!";) then the syntax is correct, but, what I would like to do is to ...
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Trying to use SNORT to alert all non-http traffic on port 80

I am using Snort 2 and I can't find anything that will specifically rule out the HTTP traffic so that I can alert for any other traffic coming in (or out) on port 80.
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Is there an easy Snort rule to CVE mapping database somewhere?

I feel like should be an easy way to map between SNORT rules and associated CVEs. I'm aware of their own search function on their site at: https://www.snort.org/rule-docs, but I feel like it's giving ...
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124 views

Snort Content first 3 bytes the same then create an alert [closed]

I was wondering if you could add into a snort rule the ability to only alert if the first 3 bytes match. I think I need to edit the content in my current rule content:"|37 e1 a4|"; I can add the full ...
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503 views

How to create content rule in Snort

The aim is to detect, if anyone in the HOME_NET is searching for a particular term - say "terrorism" and generate an alert via a content based rule. I am using Snort 2.9 installed in a virtual ...
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127 views

error read-file in snort when reading back pcap file

I get this error when using snort -r to read a saved pcap file and apply snort rules on it. ERROR : pfring daq does not support read-file I am running snort in Security Onion I tried many things: ...
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359 views

Explain this snort rule [closed]

Please explain the following Snort rule. Describe the meanings of all the options and modifiers used in the rule alert tcp $EXTERNAL_NET any -> $SQL_SERVERS 1433 (msg:"Attack Detected"; flow:...
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95 views

Snort rules to detect metasploit's trojan [duplicate]

I'm currently working on Snort and I'm trying to detect meterpreter sessions in reverse TCP or HTTPS, a Trojan ... Does anyone know snort rules in order to detect this? Despite my research, I found ...
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532 views

Can Snort inline/blocking mode block traffic from one host to another on internal LAN?

I'm putting Snort on a wifi router. My understanding is when in inline/blocking mode, I have to bridge a LAN interface to the WAN interface for packet inspection. If this is the case, it does not seem ...
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226 views

Stateful detection in Snort

From whatever I have read of Snort, it can analyse a single packet at a time and raise an alert based on its rules. What if I wish to have a rule based on multiple packets such as analysis of a ...
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65 views

Confusion Matrix for Generated Signatures in Snort

How do we come with True Positives and False Negatives rates when creating signatures in IDS? How do we measure the signatures efficiency? I've seen so many papers that discuss the same, but how do ...
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285 views

OpenAppID with Snort on pfSense [closed]

I'm using OpenAppID with Snort on pfSense, it actually work but when I view some script detector, it just detect by http pattern, which I can replace by using snort rule (with "content" option). So ...
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3k views

Snort rule for syn flood attacks - Limiting number of alerts

So I have a snort rule that detects syn flood attacks that looks like this: alert tcp any any -> $HOME_NET 80 (msg:”SYN Flood - SSH"; flags:S; flow: stateless; detection_filter: track by_dst, ...
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658 views

How to analyze .pcap file to write a generic snort rule to detect c&c activity

I am diving into snort and trying to figure out what everything does but I'm having a little trouble. I have a .pcap file I want to analyse and I know there is malicious c&c traffic on it. (...
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1answer
374 views

Is there a way to change the format of the output from snort?

I'm pretty new to snort and don't know too much about it. I am trying to put together a report of my snort files but, I only want the connections not the entire flows. For example, say I have a few ...
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2answers
6k views

Create a snort rule that will alert on traffic on ports 443 & 447

Using the learning platform, the subject is snort rules. Question is: Create a snort rule that will alert on traffic with destination ports 443 and 447. My attempts: alert tcp any any -> ...
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751 views

How to determine TLS traffic in snort signature

I am trying to have a snort signature that can detect encrypted traffic but I am not able to determine the TLS traffic using a snort signature. The content keyword search in the payload of the packet,...
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1answer
487 views

Are these snort alerts false positives or attacks?

Can anyone describe this alert please? I am confused if an attack is run against my network or not. I run snort IDS/IPS through a pfsense firewall.
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187 views

In Snort for Windows, how do I limit log file size, keep that file, and make another file instance

I have Snort for Windows. I am trying to make a log file of say size limit 1MB. When the log file hits the 1MB maximum, I want it to close that file (snort.log.1234567890) and open a new log file ...
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3k views

Threshold for DDOS Attack

I am trying to understand and simulate SYN Flood DDOS attacks. I am using snort to give me alerts. While I have control over the rate for my testing, I am interested in knowing what a good estimate of ...
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973 views

How to sniff VPN traffic using Snort?

Here's what I want to do: I want to use a VPN client on my PC (like TunnelBear). Then I want to use Snort to sniff traffic before it's encrypted and after it's decrypted by VPN. So basically I want ...
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604 views

Loopback with Suricata

Is there any way of analyzing loopback traffic with Suricata? I am trying it this way without success: root@security-onion:/home/sar/TFM/alerts/suricata# suricata -c /etc/suricata/suricata.yaml -i ...
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611 views

Analyzing Apache log with Snort

I need to analyze an Apache log with Snort and others IDS/WAFs (Suricata, mod_security and Shadow Daemon). In order to do so, I was thinking about create TCP packets with the GET and POST requests ...
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408 views

Are these Snort rules correct?

I wrote this rule so that when there are more than three failed SSH connection attempts that there is an alert but it is not working. Are these rules badly written? Or if not I ask the exact writing ...
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194 views

Snort not working with IDSWakeup

I have setup Snort with the registered user rules installed. I tested first by making the following rule in local.rules: alert icmp any any -> $HOME_NET any (msg:"ICMP test"; sid:10000001; rev:...
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674 views

How can I get Suricata to alert on 1 packet every time

I am trying to write a Suricata signature for testing purposes to alert every time it is triggered with a single PCAP file containing a single packet, but this is proving to be harder than I thought. ...
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4answers
1k views

Benefit of using two network interfaces for intrusion detection system

What is the benefit of using two network interfaces (management interface and sniffing interface) for an IDS such as Snort? I have used a Snort IDS where it only used one network interface for both ...
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795 views

how to write a snort rule to alert traffic that does not find any matched rules

Snort in IDS mode: If there is some traffic that does NOT find any matched rule against all existing Snort rules, how would you write a bottom rule to alert this traffic?
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618 views

pcap files for simulated attacks on SCADA systems?

I need to get hold of some pcap files belonging to a simulated attack on SCADA systems. My goal is to then use Snort for the detection. Or if somebody can suggest a practical environment to create my ...
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908 views

Snort.log output as unreadable symbols

I have recently installed Snort IDS on Linux Ubuntu 16.04LTS (not server), after experimenting and testing configuration in VitualBox. After installing and successfully validating the configuration ...
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419 views

How do I map the information in snort u2spewfoo output to the rule which triggered the alert?

I have a snort log file in unified2 format and I am able to view the output using the u2spewfoo utility. I think that I understand the generator id, signature id, and revision tell me why the alert ...
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2answers
1k views

Snort Exercises

I am beginning to study Snort rules and the teacher give to us the next exercises: A server on which Snort is installed is monitoring all traffic on subnet 172.16.0.0 with mask 255.255.0.0. From now ...
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snort add more data in alert file

I want to add more data to alert file rightnow the data what our analyst team see is very minimal and we are not giving access to them to our snort backend server, our design is like centos /var/log/...
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4k views

Snort priority range

What is the range of values for the 'priority' parameter in a Snort rule? The documentation it doesn't make it clear: The priority tag assigns a severity level to rules. A classtype rule assigns a ...
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511 views

Security Onion VMWare + OpenWRT IPTables Mirroring

I'm trying to set up SO in my home network to lab and see if I can monitor all ingress/egress traffic from my SOHO router. I don't have a switch with SPAN ports, or a network tap so I'm using OpenWRT ...
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2k views

How to detect a string in HTML with Snort?

I am trying to detect a string in HTML (already unzipped) with Snort. I set this rule to find content 7038685658 in my Apache web server's HTML: alert tcp any any <> any any (msg:"cell"; ...
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3k views

IDS Snort rule to catch Slow-Loris

I'm trying to write a rule to catch a Slow-Loris attack, this is what i have - alert tcp any any -> any any (msg:"Possible Slow Loris attack"; classtype: denial-of-service; flow: to_server, ...

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