[Snort-users] Snort against DARPA Dataset

Robert Vineyard vineyard at ...15653...
Fri Jun 29 11:49:19 EDT 2012

On 6/29/2012 11:22 AM, Sravan Bhamidipati wrote:
> 1. Portscan.log: The default Snort logs do not contain sfportscan alerts. Is this by design or can this behavior be changed? I am using the preprocessor's logfile option for portscan-related attacks. How reliable are the port ranges and open ports in this log? Do they identify all ports or only a few ports?
> 2. Detection rates: I am using the 3-tuple (date, source IP, destination IP) as matching criteria for portscan-related attacks (portscan.log), and the 5-tuple (date, source IP, source port, destination IP, destination port) as a matching criteria for all other alerts. I see more than 30% of the labeled attacks going unidentified by Snort. Is this matching criteria correct or in some way too liberal or stringent?

IMHO, port-scan detection is much more easily and efficiently done using netflow analysis tools. I could be wrong, but I'd guess that's why you don't see a lot of feature enhancements to that preprocessor these days.

> 3. Ruleset: How different are the Snort subscriber's ruleset, Pulled Pork rules, and Emerging Threats ruleset? Would the detection rates improve if I used all rulesets together? (As I understand Snort ignores the older or duplicate rules.) In general are older signatures (from 1998/99) ever removed or only replaced by newer signatures in these rulesets?

Pretty different. There will inevitably be some overlap, but Pulled Pork can help you sort things out. It really depends on what you're looking for, so it's hard to say if one is "better" than another. If you're looking for *everything* then you're talking at least 40,000 rules - combining GPL + VRT + ET, and that's not even counting options from other third parties. To make that happen, you're going to need a ton of RAM, and some fairly significant horsepower to chew through that many signatures.

I would say that with a task like that, your first job is to not drop packets. However, since you're replaying canned data, you already have the luxury of a 100% capture rate :-)

> 6. Is it fair to test any IDS against such old datasets?

Are those attacks still seen in the wild? If so, then a modern IDS should be able to detect something from 1998 with no problems.

Just my 2c.

-- Robert Vineyard

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