Analyze Unit42 blog post, measure coverage and propose new attack techniques

[christophetd]

https://unit42.paloaltonetworks.com/cloud-virtual-machine-attack-vectors/

[siigil]

Based on this writeup, created the following issues to track new attack techniques that are not yet covered:

• New attack technique: Login via AWS EC2 Serial Console #531
• New attack technique: Modify Startup Scripts in Azure VM Custom Data #532
• New attack technique: Login via Azure Serial Console #533
• New attack technique: Use GCP OSConfig (VM Manager) to Execute Code #534
• New attack technique: Update GCP Compute Metadata to Push SSH Keys #535
• New attack technique: Use GCP OSLogin to Push SSH Keys #536
• New attack technique: Modify Startup Scripts in GCP Compute Metadata #537
• New attack technique: Lateral movement through GCP Serial Console #538

Additionally, added a comment to #487 to note that this technique was mentioned.

4 AWS + 3 Azure techniques are already covered, will be creating a PR to update these techniques with a reference to this writeup.

[christophetd]

Looks great, based on this it sounds like we can close this issue?

[siigil]

Opened PR for documentation update, ok to close.