Cortex XDR Remote account enumeration

[LukasB]

Hello,

today we have interesting alert

At least 33 distinct non-existing accounts failed to remotely log in to XX-Laptop1. Users list: name.user, user name, user.name, username

User has no idea - all day at school, behind NAT. What I cannot really understand how terminal service can be used when is user behind NAT and there is no port forwarding and any kind of redirect.

Any idea what to check next?

src. IP adresses looks ok via Virus Total

95.143.188.128
95.143.188.126
95.143.188.122
95.143.188.129

[LukasB]

Ok, so the user was not behind NAT, but school Campus with /20 subnet.
Can anyone explain me, why cortex says the SRC_HOSTNAME = MSTSC.EXE? Does it makes sence?

Probably the FW is not switch to the public, so we will have to investigate the GPO.

[LukasB]

We found out that GPO for local firewall was disabled, so once the laptop left domain, it did not switch to the public profile...

[Rashele-Shoun]

Thanks for posting this! This reaffirmed my analysis of a very similar issue!