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In this case I tell r2 to give me the XREFS for every function that contains “_is_”. You can run any command on a for-each loop using For example, with axt can get the XREFS to any function containing the search term in one go. Here’s a useful powertrick for those already comfortable with r2.
Many commands in r2 support tab expansion Getting help on radare2’s axt command > axt sym._is_debugging We can see that some of these only have a single cross-reference, and if we dig into these using the axt commmand, we see the cross-reference (XREF) for the is_virtual_mchn function happens to be main(), so that looks a good place to start. Some of EvilQuest’s suspected anti-analysis functions Looking through our text file, we can see there are a number of function names that could be related to some kind of anti-analysis. Let’s run afll as we did when analyzing OSX.Calisto previously, but this time we’ll output the function list to file so that we can sort it and search it more conveniently without having to keep running the command or scrolling up in the Terminal window.
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A Faster Way of Finding XREFS and Interesting Code Yay, attach success! Let’s take a look around before we start diving further into the debugger. The problem is that we need elevated privileges to debug, so a simple sudo should get us past our current obstacle. That ptrace: Cannot Attach: Invalid argument looks ominous, but actually the error message is misleading. We already removed the extended attributes and codesigning isn’t the issue here, but the radare2 debugger fails to attach. Unfortunately, our first attempt doesn’t go well.
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We’ll remove the extended attributes to bypass Gatekeeper and Notarization checks with % xattr -rc Īnd we’ll attempt to attach to the radare2 debugger by adding the -d switch to our initialization command: % r2 -AA -d patch If we need the sample to be codesigned for execution, we can also sign it (remember your VM needs to have installed the Xcode command line tools via xcode-select -install) with: % sudo codesign -fs -deep In this case, the sample isn’t signed at all, but if it were we could use: % sudo codesign -remove-signature The first thing you will want to do is remove any extended attributes and codesigning if the sample has a revoked signature.
However, that’s all good news for us, as EvilQuest implements several anti-analysis features that will serve us as good practice.
#Anti malware software mac os how to#
It may well have been a PoC, or a project still in early development stages, as the code and functionality have the look and feel of someone experimenting with how to achieve various attacker objectives. SentinelLabs quickly analyzed it and produced a decryptor to help any potential victims, but it turned out the malware was not very effective in the wild. Our sample hit the headlines in July 2020, largely because at first glance it appeared to be a rare example of macOS ransomware. Getting Started With the radare2 Debugger
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In this post, we’ll look at how to circumvent the malware author’s control flow to avoid executing unwanted parts of their code, learning along the way how to take advantage of some nice features of the r2 debugger! We’ll be looking at a sample of EvilQuest (password: infect3d), so fire up your VM and download it before reading on.Ī note for the unwary: if you’re using Safari in your VM to download the file and you see “decompression failed”, go to Safari Preferences and turn off the ‘Open “safe” files after downloading’ option in the General tab and try the download again. Consequently, one of the first challenges we often have to overcome is working around these attempts to prevent execution in our safe environment. Malware authors, however, may have other ideas and can set up various roadblocks to stop us doing exactly that. Along the way, we’ll pick up tips on both how to beat obstacles put in place by malware authors and how to use r2 more productively.Īlthough we can achieve a lot from static analysis, sometimes it can be more efficient to execute the malware in a controlled environment and conduct dynamic analysis. Last time out, we took a look at how to use radare2 for rapid triage, and we’ll continue using r2 as we move through these various challenges.
#Anti malware software mac os series#
In this second post in our series on intermediate to advanced macOS malware reversing, we start our journey into tackling common challenges when dealing with macOS malware samples.
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