Questions tagged [snort]

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

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Detect repeating bits with snort

I am new to snort and I am trying to make a rule that will detect repeating bits in a packet. I set it to offset to the 100th bit and the depth is 105 bits. The problem I am having is I can't figure ...
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50 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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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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Snort Rule to check for TCP options

Lets say malformed packets are sent by attacker with improper TCP options length i.e, 50bytes,222bytes etc. Is there any way to monitor these packets having invalid tcp options set using Snort or ...
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34 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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What can be wrong with this simple Snort Rule?

i'm using snort since some weeks now and today i want to use it in order to trigger alert for some content in the case of HTTP requests. So i try a simple rule like this one in order to begin.. alert ...
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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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How to run a snort rule over PCAP file in Windows? [duplicate]

I have a PCAP file from CICIDS, and what I'd like to know is how can I apply the Snortrule in Windows? I've not written any custom rules myself but want to run the rules already available. For now, ...
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677 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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2answers
139 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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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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Can an IDS be used for detecting frames (not packets) from an non-authenticated station

Can an IDS, like snort, be used to detect Layer 2 network frames from a system i.e a system is trying to send a frame to the AP and whether Snort can work on the frame based on the rules?
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Create a snort rule that will alert on traffic on ports 443 & 447

Using the Immersivelabs 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 ...
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226 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
182 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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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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Snort CSV details @ alert

I have enabled the fast logging mode, my question here is how can I extract the CVE details or reference tag inside the /var/log/alert file, as if now I am able to see only this much data in alert ...
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2k 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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398 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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237 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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294 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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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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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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263 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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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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448 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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397 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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488 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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248 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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714 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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116 views

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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2k 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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339 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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1k 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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1k 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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1answer
370 views

Suricata does not detect “self” traffic

I have built two simple rules alert tcp any any -> any any (msg: "tcp detected"; sid: 2; rev: 1;) alert udp any any -> any any (msg: "udp detected"; sid: 1; rev: 1;) Then from the same machine ...
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240 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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snort file_inspect signature working inconsistently [closed]

I am trying snorts file inspect preprocessor for blocking incoming files from their sha256sums. I am using snort version 2.9.9.0 with daq nfq inline mode any my file_inspect preprocessor configs are ...
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1answer
431 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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174 views

How to detect long lived SSH sessioned

I am trying to figure out a way to detect ssh sessions that have been established over a long period of time. I seem to recall that there were ways to detect tcp connections that have been connected ...
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2k views

Major differences between Snort and Snort 3.0

When I visited the the Snort's website to download the source code for compilation, I found there were 2 downloads available. One was titled Snort and another was titled Snort 3.0 Has the ...
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REJECT Nikto Scans With Snort Rules

Hoping someone on here knows a way to reject Nikto traffic with Snort rules. I've been having zero luck for days finding this anywhere online. Thanks. Peace.
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how to use snort to track http/https sessions separately?

how can I use snort to breakdown http/https traffic into separate sessions and track each session separately and also dump them into separate log files or something that I can read from.
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11k 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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1answer
327 views

Can I run Snort on a slow computer?

I'm trying to use a device with 1GB of RAM and a Single 800 MHz core CPU. I will use Snort to analyze traffic on my LAN network. Snort, unfortunately, cannot analyze all the traffic (sometimes it ...
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114 views

Signature Generate by Honeyd “Honeycomb” is not accept by Snort IPS

I posted this on SO [https://stackoverflow.com/questions/44652014/signature-generate-by-honeyd-honeycomb-is-not-accept-by-snort-ips] is this on topic here? What would I need to do to my question ? I ...
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575 views

Snort Alert - What is PROTO:255?

My Snort alert output is like below. The first element of 4th row of each alert indicates Protocol. However, in the alert (portscan) TCP Portscan, the protocol is PROTO:255. What does it mean? Why ...
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309 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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220 views

How to log only the TCP header using command line in snort or nmap? [closed]

I work with snort log file and now I need to extract the TCP header. My question is: How to log only the TCP header from the packets captured by snort log file (without the payload) using command ...
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2answers
3k views

How does the flow option of Snort work?

For example, flow:established is detecting only for packets with sessions connected. Then, the server is rejecting packets to received after the session is disconnected?