Add NightshadeC2, MonsterV2 Yara Rules

[YungBinary]

• Add NightshadeC2 Yara rule, see https://x.com/YungBinary/status/1963751038340534482
• Update MonsterV2 yara rule to work for b869941a9c476585bbb8f48f7003d158c71e44038ceb2628cedb231493847775 and 666944b19c707afaa05453909d395f979a267b28ff43d90d143cd36f6b74b53e
• Fixed symlink check in kvm-qemu.sh, "-L" argument should be used instead, fixes error:

ln: failed to create symbolic link '/usr/bin/qemu-system-x86_64-spice': File exists
ln: failed to create symbolic link '/usr/bin/kvm-spice': File exists
ln: failed to create symbolic link '/usr/bin/kvm': File exists
[-] Install failed

• Fixed missing qemu directory, create it first to fix error:

[-] Bios patching failed

[gemini-code-assist]

Summary of Changes

Hello @YungBinary, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the repository's threat detection capabilities by integrating a new YARA rule. The addition aims to improve the identification of the NightshadeC2 malware, contributing to more robust security analysis.

Highlights

• New YARA Rule for NightshadeC2: This pull request introduces a new YARA rule, NightshadeC2, specifically designed to detect the NightshadeC2 malware.

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[gemini-code-assist]

Code Review

This pull request adds a new Yara rule for NightshadeC2. The rule is a good starting point, but I've identified a couple of issues that should be addressed. The description URL in the metadata is incorrect, and the rule is missing the standard cape_type field. Additionally, the file is missing a final newline character. I have provided suggestions to correct these issues.

[kevoreilly]

Would it be possible to have more than one pattern for the yara?

I would say two or three patterns per yara is preferable as it's far less brittle and more future proof.

[YungBinary]

Would it be possible to have more than one pattern for the yara?

I would say two or three patterns per yara is preferable as it's far less brittle and more future proof.

Okay got it, added more patterns for NightshadeC2 AKA CastleRAT

[kevoreilly]

Are the changes to installer/kvm-qemu.sh intentional?

[YungBinary]

Are the changes to installer/kvm-qemu.sh intentional?

Yes the script has bugs in it that these changes fix, see my PR notes:

Fixed symlink check in kvm-qemu.sh, "-L" argument should be used instead, fixes error:

Fixed missing qemu directory, create it first to fix error:

[kevoreilly]

I spent a few hours trying to improve the MonsterV2 yara with two more patterns as per my previous suggestion.

Alas I did not find good enough patterns in that time that cover all samples.

Because this issue has held the PR up so long I am giving up and merging, but ultimately I am not satisfied with the detection here as it is to brittle. It would just be a greater disservice to delay the other improvements longer, but the detection still should be improved.