Questions tagged [snort]

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

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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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2answers
221 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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Open source or common implementations for reverse proxy web application security

I realize there is already a question similar to this one, but this is somewhat of a follow-up. I understand that a reverse proxy server by itself is hardly useful as a web app security measure ...
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1answer
486 views

Snort false positive, yet suspicious

I have Snort installed and tuned nicely with ET Rules on my pfSense, both my pfSense and the modem are using Googles public DNS 8.8.8.8. Recently I was denied access to google.com, and by reviewing ...
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53 views

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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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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1answer
401 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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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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2answers
316 views

Can dual NIC Snort machine cause threats to bypass firewall?

I am thinking about building a Linux Snort machine that can listen to both WAN and LAN traffic. Setup I am thinking about: Snort computer with two NICs One NIC connected to hub/tap outside firewall (...
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4answers
15k views

Can Snort run on a Raspberry Pi?

I am in the preliminary stages of designing a cybersecurity suite for my home network. I don't have any servers or anything, just the standard home setup (computers, tablets, game consoles). The ...
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0answers
550 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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42 views

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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724 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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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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2answers
4k 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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925 views

Question on SNORT Rule

I am new to SNORT and can not figure out what the following rule means: alert tcp $EXTERNAL_NET any-> $HOME_NET any (msg:"SCAN FIN"; flags: F; reference:arachnids,27;
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1answer
17k views

How to run a snort rule over pcap file

I have a pcap file, and what I wanted to know is how can I apply the Snortrule below which I've already written within the rules folder in my log folder: alert icmp any any -> any any (msg:"TCP ...
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839 views

Security Onion: Snorby alerts show all local network source IP (public and private)

I have recently installed the Security Onion distro for Ubuntu. This distro does a great job of combining multiple tools like snort/Suricata, Sguil, Snorby, Elsa, bro ids, Squert, etc. Within my ...
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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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Snort stops generating alerts when HOME_NET changed to public addresses

I have used snort for traffic analysis quite often and it worked fine as it generates rules that are corresponding to packets doing malicious activities on my HOME_NET which is always private ...
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1answer
261 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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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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218 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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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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144 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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413 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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189 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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1answer
58 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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2answers
7k views

How can I read snort logs in NIDS mode?

I am reading some snort logs from a firewall, I could read some with "snort -r file" But when I had tried the newest logs I get this error: snort -r snort.log Running in packet dump mode ...
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1answer
204 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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5answers
62k views

Testing Snort IDS installation

What is the easiest way to test Snort IDS after installing? Would using and writing a rule that captures all of the traffic work? alert ip any any -> any any ( msg: "ICMP packet detected!"; sid: ...
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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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389 views

Detecting Guest to Guest Traffic in Virtualbox Using Host Running Snort

Not sure if this is a simple question but I was hoping for some insight into finishing a pentest lab. My goal is to have Snort sniff an attack in a virtual environment between two guest VM's. My ...
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2answers
455 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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604 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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Snort gives “could not create the registry key” error for multiple kinds of operations

I've set up a host-only network in Virtualbox consisting of a Kali linux machine and a Windows 7 machine (the host is running OS X). I have Snort installed on Windows 7 and am attempting to verify ...
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3answers
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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1answer
629 views

Snort: Cannot decode data link type 127 reading a pcapng file

I've captured on my wifi some days ago and now I want snort to analyse the capture to detect any problem. However, when I run snort -l ./snort-log -b -c /etc/snort/snort.conf -r captura-analisar....
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489 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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1answer
508 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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311 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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1answer
2k views

Snort rule does not work when combining “content” fields

I'm trying to write a snort rule which outputs an alert whenever a web server returns an HTML document containing a specific string. I've come up with the following rule: alert tcp any any -> any ...
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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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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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1answer
355 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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701 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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1answer
554 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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1answer
10k views

Snort/IDS detect and alert on possible DoS/DDoS attack?

As per the title, I'm attempting to configure Snort to detect and alert on a incoming Denial of Service attack. Looking at the rulesets, which are primarily signature based rules, I can't see a ...
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751 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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1answer
625 views

Use Snort to limit or prioritize application bandwidth usage [closed]

Short version of a long story, we've been using bluecoat packetshapers for bandwidth control on a multi-tenant network. We like it because it allows us to divide the bandwidth equally, but still allow ...