Network Intrusion Detection Systems Fail to Impress

TheBongPipe writes "I'm reading a nice test here about 7 commercial IDSs. Who won the prize? Nobody..." They also looked at Snort, but found that all the products generated way too many false alarms.

Comments

Snort and GUI

[fabiolrs]

I had a nice experience using snort.

Come on, reading the article I saw the guy said a Snort disadvantage is not having a GUI. What kind of technical user this guy is? :/ Point and click is not always the best solution...

Need more detail

[seosamh]

It'd be nice to have some more detail on their results. The chart on the page shows Snort detected all the attacks listed in the chart except the SYN flood. And the footnote on that entry says Snort was down because of "configuration error."

Gee, whose fault is that?

A False Alarm is still an Alarm

[pheph]

I worked in a NOC for some time and found that while false alarms generally take away from the impact of real alarms, they still alarm you that something not quite right is going on in your network.

They also go on to mention all ask too much of their users in terms of time and expertise to be described as security must-haves. IDSs are not screen-savers. Those who are setting up an IDS better have a good understanding of how they work and how to configure these applications. Point-and-click doesn't really apply to something this involved.

... As for stability, I think this report is correct, the only IDS I've used that didn't crash consistanty was snort (with ACID)

Car Alarms

[Codex The Sloth]

Like Car Alarms, if it goes off all the time, people will just ignore it -- At some point, the noise drowns out the signal.

You would hope that the increase in false positives decreases the number of false negatives but that isn't necessarily true either.

Re:False Positives...

[sam_handelman]

Well, that's true, unless

ALERT: Intrusion attempt detected! User Liora mistyped his password!

the rate of false-positives is high enough that

ALERT: Account Liora has recieved login attempts from three different IPs in the past 12 hours!

you stop paying attention; unlike with AIDS testing (which has a very high false positive rate) the user is simply likely to ignore the system even if real threats occur

ALERT: 1,262 attempts to login as user "root" in past 7 seconds!

So it becomes desirable to lower the false positive rate to a manageable level, WHATEVER the rate of false negatives is, because otherwise you won't actually catch anything.

The purpose of the AIDS test is to assure you that you don't have AIDS. False negatives are unacceptable, false positives can be dealt with.

The purpose of the IDS is not to prevent intrusions - that would be nice, but it's not going to happen. The purpose of the IDS is to identify the (coloquially) hackers, so that you can retaliate against them / deter them, before they get you too many times, or get too many different people once. To do this, you need a deterence-level set of positives which is small enough (and true positive rich enough) for you to actually act on them.

Oh, and because I get off on it when people with agree with me: this is no substitute for real, human-level, security measures. Someone who expects any system of this kind to protect them from lousy sysadmin decisions deserves the rusty metal sodomy they will no doubt recieve.

The problem with false alarms

[why-is-it]

Too many false alarms isn't necessarily a bad thing. In intrusion detection you'd rather take the false positives, than the alternative.

Spoken like someone who does not carry the IDS support pager at nights and on week-ends!

The problem with too many false IDS alarms is that the staff tend to treat it like the boy who cried wolf. After awhile, you disregard the pages or treat them with less consideration because the last n pages have all been false alarms.

I think that IDS is important, but if there are too many false IDS alerts, it becomes difficult to put up with. Because they are strictly reactive systems, it is improbable that there will ever be a perfect IDS that never raises false alarms, but clearly there is a lot of work to do. I am surprised that Snort did so poorly, since it really is a nice system, but it takes a long time to build up a good set of heuristics...

The rate of false fire alarms, and false burgular alarms is VERY high compared to the actual number of real emergencies.

That's right. And in my area, if the police department are called out to the same location for three false burglar alarms in one year, they will not respond to any subsequent alarms automatically. And the fire department charges a fine of $300.00 per incident if they receive more than three false fire alarm calls to the same location in one year. Why? Because, as you said, the number of false alarms is much higher than the number of actual emergencies. The false alarms cost time and money and if all the resources are busy dealing with false alarms, there is nobody left to help when a genuine emergency occurs.

Clueless reporters

[Python]

After reading this report, I'm left with the impression that the reporters that wrote it had unrealistic expectations for the products they deployed, and little knowledge about either how to configure, tune or properly setup the products they were testing. But then, they admit that everything they are complaining about isn't such a big deal and so on. In short, a totally sensationalized waste of time. Skip it if you haven't read it already.

To wit, we've used all of the products they complain endlessly about, and all I can say is RTFM. All of the problems they encounter are either configuration problems or worse, PEBKAC.

If you want to really learn about IDS, and you don't have the budget to buy a commercial IDS, download a copy of snort and learn for yourself. This report strikes as the type of complaing you get from an IT customer that wants to buy a product, turn it on, never configure it and expect it to magically work.

By now, readers with security expertise probably are asking why we didn't tune the IDSs to reduce the chatter and improve our chances of seeing real attacks. The short answer is that we did, or at least we tried to (emphasis added). Including setup time, this project stretched along three months; and during that period we worked on these systems almost every day.

Wow! What a revelation! You mean you have to know what you're doing and it actually takes time to configure these powerful tools?! In a word, DUH. IDS'es must be tuned. IT products must be configured properly. These things take time, sometimes a lot of time. The core of their complaints revolve around their inability to do either of these things well. Given that lots of people manage to do this effectively everyday and have been for years and years, we're left to conclude that these reporters were not up to the task. And here it is:

Don't expect IDSs to be plug-and-play devices.

These folks actually expected NIDS to be plug-and-play, and thats what they seem upset about. NIDS are powerful sniffers, they need to be tuned, they need to be configured and yes, this IS an ongoing process - but they are not plug-and-play devices.

Futhermore, all of IT is an ongoing process. A big, circular, ongoing process that requires competent personnel to manage, maintain, tune, test, patch, configure , deploy and yes, spend TIME on. Anyone that expects to be able to deploy close to a dozen different IDS products as plug and play devices into a production network in 90 days with questionable expertise is fooling themselves.

To be effective, they require a lot of tuning, and a fair amount of security expertise (emphasis added). They'll also require willingness to spend a lot of time sifting through reports, at least until the configuration is tuned properly. Even then, IDSs will require constant updating as new attacks appear. IDSs can be lifesavers and invaluable educational tools - but only for those with a lot of patience and a willingness to learn.

And then they say as much. Again, this report is total waste of time. Its overly sensationalized and stems from a lack of expertise on the products in question. Skip it, download snort or buy one of the commerical products, take a class, read a book and learn for yourself. You won't learn much from this report that common sense wouldn't have told you already.