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Interview with Jim Aldridge on Targeted Intrusion Remediation. Part 2

In this subset of questions & answers, Mandiant’s Jim Aldridge sheds more light on the typical targeted attack lifecycle and the key countermeasures to adopt.

– A lot of successful targeted intrusions have involved various red herring techniques. For example: some systems are DDoSed and while all the security guys work on it, a spear phishing is used to get in from another end. Do you see this as a growing issue?

– In my experience, attackers have no need to create a diversion. Most organizations fail to detect targeted intrusions.

– How difficult is it to find all of the attackers’ entry points?

– Academically speaking, we could build a list of all the potential ways you could get code to execute on a particular computer system and that would equal all the entry points. On a typical Windows system, there are dozens of executable files that may load hundreds of libraries. All of these are potential entry points. A global corporation with thousands of servers, dozens of business partners and hundreds of suppliers – each with entry points of their own – could potentially have hundreds of thousands of entry points.

All indications of attacker activity must be investigated thoroughly to find the actual entry points.

For example, if you’re an IT administrator, and have just noticed an antivirus alert for “pwdump” on your domain controller, you could hit the “clean” button and move on with your day. I’ve seen organizations take that approach and it doesn’t work.

Or, you could ask yourself how “pwdump” came to execute on that system. Perhaps two seconds prior to that file executing, a particular user account logged into the system. Then you would find out from which system that connection originated then take a look at that system. Perhaps there you would find a backdoor. As you investigate, you identify indicators of compromise, for example attributes related to the “pwdump” file, the name of the account used to log on to the domain controller and the registry key that the backdoor creates to maintain persistence.

If you want to understand all the entry points, you would continue that process iteratively until you had a complete story that explained how the attack happened. In the process, you would also have determined the information you need to successfully remediate.

Targeted attack lyfecycle

Targeted attack lyfecycle

– You mentioned attackers follow specific sequence of events. What types of dedicated attackers usually follow steps described in your “attack lifecycle”, and can you describe an attacker who doesn’t?

– In my experience, most attacks follow at least some subset of this lifecycle. Targeted attacks will typically include multiple phases. More simplistic attacks will follow less phases, for example just an initial intrusion and the theft of data.

– What to do if an organization does not recognize a targeted intrusion and uses standard whack-a-mole method? How difficult is it for them to quickly embrace the need to shift to your method?

– In my experience, it depends on management’s willingness to try a different approach. Often, an organization needs to experience the frustration of an ineffective approach first. A knock on the door from law enforcement, a frequent method by which organizations find out that they have been compromised by a targeted attacker, can also be a big motivator.

– Is poor visibility across systems a huge problem? To what extent do most organizations in your experience have visibility?

– More organizations have poor visibility than have good visibility. By poor visibility, I mean that they do not have the necessary processes and technology to know what traffic is exiting their network, or what indicators of compromise may be present on their systems. From a systems perspective, their primary means of visibility consists of antivirus tools, which provide limited capabilities.

– Why do organizations lack visibility? Is it expensive or does it require specific skills and experience?

– Most organizations “don’t know what they don’t know”. Implementing the right tools, and more importantly, having the right people to make use of the information, requires investment. It can be difficult to convince leadership of the need for such investments. After a targeted intrusion, it is typically easier to make the case for those investments.

– What is the weakest part in the attack lifecycle? Where do you usually start running countermeasures and are always successful?

– I don’t think that it’s possible to always be successful with a countermeasure. Take application whitelisting, which is one of my favorite countermeasures. Consider the example of an application whitelisting tool that has properly been implemented on a domain controller. Even if an attacker gains domain administrator privileges, he should not be able to run a password hash dumper on the domain controller. This is typically effective.

However, the Achilles Heel in that equation is the trust placed in the certificates, which is one of the ways the tool determines whether a program is allowed to run. When you configure the whitelisting tool, most users decide that rather than trusting thousands of Microsoft executables and libraries, they will just trust all files signed with a valid Microsoft digital certificate instead. This provides advantages from an operational perspective since it makes patches and updates easier; if you trusted the files instead of trusting Microsoft, you would have to trust all new files at every update.

A determined attacker that is able to compromise a certificate and sign malware, making it look legitimate, can defeat that countermeasure (I still strongly recommend application whitelisting: no countermeasure is perfect).

I don’t see any parts of the lifecycle that are relatively more challenging than others from the attacker’s perspective. Escalating privileges may take some time and effort, particularly if the initially compromised system doesn’t immediately provide the attacker with privileged credentials. The key from a defensive perspective is to make as many of the pieces as difficult as possible, which provides more opportunities and time to detect and contain the intrusion.

Read previous: Best Practices of Targeted Intrusion Remediation: Interview with Mandiant’s Jim Aldridge

Read next: Interview with Jim Aldridge on Targeted Intrusion Remediation. Part 3

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