Despite continuing promises from software vendors, malware isn't going anywhere. Analyzing malware to protect against it and repair the damage that it may have done, is a significant part of the job description for many security professionals. The sheer volume of malware can make dealing with it an overwhelming task. Fortunately, a number of free cloud-based services have emerged to aid in the task of analyzing malware.
I'll divide the analysis tools into two categories - Anti-Virus Multi-Scanners and Sandboxes. The former is nothing more than a collection of AV scanners designed to run together analyzing the same file and return the different results for each AV vendor. This can be a very valuable starting point. It is frustrating to spend hours or days conducting deep analysis on a new binary only to find out that AV vendors have already analyzed the same file previously. A quick run through a multi-scanner can help to let you know if you're dealing with 0day or yesterday's news. Sandboxes on the other hand are emulation environments which perform automated behavioral analysis on a binary file. They allow the binary to execute and emulate the services that it attempts to interact with. Meanwhile, they are recording the activity which is occurring such as file reads/writes, registry access and network traffic.
Building your own multi-scanner isn't a terribly difficult or expensive challenge. You need to obtain AV SDKs or command line tools from various vendors, develop a wrapper/front-end to simultaneously submit the same malicious code samples to all at the same time and parse/combine the results into a meaningful report. While it may be valuable to put in the effort if you expect to feed a heavy and regular volume of binaries into the multi-scanner, say for a honeypot network, there are free online alternatives if you're looking for only occasional analysis. Below is a chart comparing the functionality of a couple of popular (and free) multi-scanners.
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Sandboxes automate the process of behavioral analysis. They permit a binary to execute in a controlled environment and monitor the activity which occurs. Given that we're dealing with malicious code, the binaries will generally attempt to spread, often by scanning for vulnerable hosts. Rather than actually permit malware to spread externally, sandboxes can simulate network responses to allow the binary to continue executing without actually permitting third party infection. If a steady volume of analysis is required you'll want to consider commercial products such as those offered by Norman and Sunbelt Software, however, such solutions can be expensive. If you only require periodic analysis, both vendors offer free web based access to their platforms. Anubis, by contrast, is purely a free web based service and does not have a commercial product offering. The chart below compares the functionality of these three cloud based sandboxes:
As can be seen, for an entirely free service, Anubis has an impressive feature set. They even encourage the automated of binaries for analysis so the platform can even be integrated into a honeypot network.
It's great to see free resources emerging for malware analysis. As mentioned, these free services won't meet everyone's needs, but if you're tasked with securing a network and only occasionally need analysis capabilities, these sites can significantly streamline your efforts.