Feeds

Time to blacklist blacklists

Plenty of ways to overcome 'minor inconvenience'

3 Big data security analytics techniques

Blacklists have their place for detecting and identifying malicious content and activity, with the whole signature-based malware detection industry effectively being built around the concept that blacklists are reliable mechanisms.

The only problem is that they aren't.

They certainly are an important element of security models, but the last couple of decades of security research has shown that they quickly become ineffective in the face of a rapidly evolving threat.

Early in the life of antivirus tools, simple signature based detection was enough. An internal blacklist could identify all known pieces of malware because they did not evolve or spread very rapidly. When polymorphic malware began to exhibit better software development, the need for heuristic detection engines became more urgent. Most antimalware software now has a combination of blacklisting and heuristics in use to assist in identifying malicious activity (when they aren't busy deleting critical system files or being compromised by their own analysis engines).

Having an exhaustive blacklist helps companies claim that they detect many tens of thousands of viruses and malware, when in reality it may be many different versions of a few key pieces of malware, just different enough from previous versions to require a brand new blacklist signature.

Moving on to blacklists of known spam-generating IPs and malware-serving sites, we start to see significant problems emerge with this particular approach to protection.

Many mail server administrators will have encountered at least one period where they have found their IP on an RBL (Real Time Block List) alongside IPs that have seen to be spewing spam across networks (or they could have just had AOL mailing list subscribers who find it easier to report as spam than unsubscribe from something they manually subscribed to). With the use of dynamic IP addresses and virtual hosts, many have found that if they have a bad network neighbour, they can be hit with the same blocking (we've had it happen a few times) from indiscriminate RBL maintainers.

Even important registries are not immune from arbitrary blockage and ongoing annoyance from poorly developed RBLs.

The problem of misidentification becomes even worse when blacklists of websites that are hosting malware and phishing attacks are maintained. Microsoft, Mozilla, Opera, McAfee, and Google are just some of the large bodies that have invested significant resources to the creation, maintenance, and use of website blacklists to warn users of potential malicious activity on websites (and in some cases prevent access).

Anyone who spends even just a little bit of time involved with researching and observing the patterns and pace of website attacks, hacks and defacements will know that websites are essentially fragile entities and it doesn't take much for a well-trusted site to become a malware-spewing nightmare.

Like trying to use DRM to restrict the spread of copyright infringement, using blacklists / blocklists to limit access to sites will only stop the honest, and the casual attacker (extremely casual attacker) from getting people to see their site. Any attacker that is remotely serious about their work will have plenty of ways to bypass and overcome the minor inconvenience that the blacklists pose.

If any further evidence was required, a security researcher (Kuza) has published a small set of techniques that can be used to bypass these website blacklists. The set of techniques published reflects just a small number of the many different ways that it is possible to avoid these lists, not least of which is the fact that it takes time for a site to be added to a blacklist.

The response that Kuza received from Microsoft when he reported his techniques for phishing detection avoidance is actually quite an intelligent response - "[it] is not a security feature".

The only problem with this is that many, many people (including a lot of 'security' people who should really know better) consider these lists to be just that - a security feature.

It is time that people became aware that these lists are a small tool of their protection arsenal, and not the major innovation that their creators and maintainers describe them as. It is also time that people became aware of the problems that these lists can cause when improperly developed and maintained (and even when they aren't).

This article originally appeared at Sūnnet Beskerming

© 2007 Sûnnet Beskerming Pty. Ltd

Sūnnet Beskerming is an independent Information Security firm operating from the antipodes. Specialising in the gap between threat emergence and vendor response, Sūnnet Beskerming provides global reach with a local touch.

3 Big data security analytics techniques

More from The Register

next story
Obama allows NSA to exploit 0-days: report
If the spooks say they need it, they get it
Samsung Galaxy S5 fingerprint scanner hacked in just 4 DAYS
Sammy's newbie cooked slower than iPhone, also costs more to build
Putin tells Snowden: Russia conducts no US-style mass surveillance
Gov't is too broke for that, Russian prez says
Snowden-inspired crypto-email service Lavaboom launches
German service pays tribute to Lavabit
Mounties always get their man: Heartbleed 'hacker', 19, CUFFED
Canadian teen accused of raiding tax computers using OpenSSL bug
One year on: diplomatic fail as Chinese APT gangs get back to work
Mandiant says past 12 months shows Beijing won't call off its hackers
Call of Duty 'fragged using OpenSSL's Heartbleed exploit'
So it begins ... or maybe not, says one analyst
Heartbleed exploit, inoculation, both released
File under 'this is going to hurt you more than it hurts me'
prev story

Whitepapers

Securing web applications made simple and scalable
In this whitepaper learn how automated security testing can provide a simple and scalable way to protect your web applications.
3 Big data security analytics techniques
Applying these Big Data security analytics techniques can help you make your business safer by detecting attacks early, before significant damage is done.
The benefits of software based PBX
Why you should break free from your proprietary PBX and how to leverage your existing server hardware.
Top three mobile application threats
Learn about three of the top mobile application security threats facing businesses today and recommendations on how to mitigate the risk.
Combat fraud and increase customer satisfaction
Based on their experience using HP ArcSight Enterprise Security Manager for IT security operations, Finansbank moved to HP ArcSight ESM for fraud management.