Wednesday, November 25, 2009

Enterprise Botnets - Targeted or What?

Whats the difference between these massive botnets gobbling up sizable chunks of the Internet and those found inside the enterprise? Quite a bit actually.

Over the last couple of months I’ve been talking at a number of conferences and speaking with customers about the kinds of botnets we observe within enterprise networks as opposed to whats generally seen propagating the Internet at large. As you’d expect, there are a number of differences – partly because of the types of bad actors targeting businesses, and partly because enterprise perimeter security is considerably more advanced than that found at the end of the average DSL Internet connection.

From a cross-network visibility perspective, the types of botnets regularly encountered operating within enterprises in 2009 can best be divided (and described) as follows:

Internet Targeted – or “broad-spectrum” attack for want of a better description – account for approximately half of all botnets regularly encountered inside enterprise networks. These botnets aren’t targeted at any particular network – just at the average Internet user – but they typically manage to infiltrate enterprise networks due to lax security policies and as bleed-over from the other networks (and devices) employees may connect to. I discussed some of this in the earlier blog – Botnet bleed-over in to the enterprise – in which botnets designed to steal online gaming authentication credentials often appear within the enterprise. Just about all of these broad-spectrum botnets can self-propagate using an assortment of built-in worming capabilities. Fortunately, just about every one of these botnets are easily detected with standard host-based antivirus products.

What this means in practice however is that hosts “not quite” adhering to the corporate security policy, or which are a little behind in apply the latest patches (including not running the very latest signatures for their antivirus package), are the first to fall victim – and no organization I’ve observed in the last 20 years has ever managed implement their security uniformly throughout the entire enterprise.

I foresee that these “broad-spectrum” botnets will continue to appear within enterprises and be a nuisance to enterprise security teams. That said though, just because they aren’t targeted and fixes are available, it doesn’t mean that there’s no threat. If a particular botnet agent doesn’t yield value to its original botnet master (e.g. a botnet focused on obtaining passwords for social networking sites), it is quickly passed on to other operators that can make money from it – repurposing the compromised host and installing new malware agents that will yield value to the new owner.

Enterprise Targeted botnets are botnets that are hardly ever found circulating the Internet, and are designed to both penetrate and propagate within enterprise networks alone. Around 35% of botnets encountered within enterprise networks are this type. They are typically based upon sophisticated multi-purpose Remote Access Trojans (RAT); often blended with worming functions capable of using exploits against standard network services (services that are typically blocked by perimeter firewal technologies). Perhaps the most visible identifier of a botnet targeted at enterprises is the native support for network proxies – i.e. they’re proxy-aware – and capable of leveraging the users credentials for navigating command and control (CnC) out of the network.

In general, these “targeted” botnets aren’t targeted at a specific organization, but at a particular industry (i.e. online retail companies) or category of personnel within the organization (e.g. the CFO).The botnet agents tend to more advanced (on average) than most botnet malware encountered within enterprise networks – offering greater flexibility for the botnet masters to navigate the network and compromise key assets, and to be able to extract any valuable information they manage to obtain.

Deep Knowledge botnets are a completely different beast. Accounting for 10% of the botnets encountered within typical enterprise networks, these botnets tend to rely upon off-the-shelf malware components (more often than not, being built from commercial DIY malware creator kits). Depending upon the investment made by the botnet master, the features of the botnet agent can be very sophisticated or run-of-the-mill. What makes them so dangerous though is that the creator (who is often the botnet master) has a high degree of knowledge about the infiltrated enterprise – and already knows where to find all the valuable information. In some cases specific people or systems are targeted as beachheads in to the organization, while in others key organization-specific credentials are used to navigate the network.

Where this “deep knowledge” comes from can vary considerably. Each botnet within this category tends to be unique. I’ve come to associate these botnets with past or present employees (rather than industrial espionage) – as it’s not uncommon to be able to associate the CnC server of the botnet to a DSL or cable Internet IP address in the same city as the office or building that has been breached. In some cases I wouldn’t be surprised if the installation of these botnet agents were conducted by hand as a means of (semi)legitimate remote administration (think back to the problem in the mid-1990’s when people were installing modems in to their work computers so they could access them remotely). The problem though is that most of these commercial DIY malware construction kits have been backdoored by their creators (or “partners” in their distribution channel) – which means that any corporate assets infected with the botnet agent will find themselves under the control of multiple remote users.

Other” represents the catch-all for remaining 5% of botnets encountered within enterprise networks. These botnets (and the malware they rely upon) vary considerably in both sophistication and functionality, and don’t fit neatly in to any of the previous three categories. They include the small botnets targeted at an organization for competitive advantage, through to what can only be guessed at as being state-sponsored tools targeting specific industries and technologies.

It’ll be interesting to see how the distribution of these four categories of botnets change in 2010. I suspect that the proportions will remain roughly the same – with the “other” category decreasing over time, and being largely absorbed in to the “Enterprise Targeted” category rather than “Deep Knowledge”.

==> Reposted from

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