Windows Persistence Scheduled Tasks Obfuscation

In the great article „Securonix Threat Labs Security Advisory: Detecting STEEP#MAVERICK“ D. Iuzvyk, T. Peck, O. Kolesnikov reverse engineer an attack campaign where some windows scheduled tasks are used for persistence with some obfuscation for evasion of security detection:

Quote of the passage:

„Stage (7): Persistence – Scheduled Tasks

The script also attempts to embed itself as a scheduled task on the affected host. The task names itself one of two names depending on the permission level:

  • MicrosoftEdgeUpdateTaskMachine_System
  • MicrosoftEdgeUpdateTaskMachine_User

The task is created using some clever obfuscation to hide the call to “schtasks.exe”. It uses an invoke expression mixed with wildcard matching so “$env:???t??r???\*2\??h???k?*” translates to “$env:SYSTEMROOT\System32\schtasks.exe”.

The task is designed to run the exact same script that we noticed in the registry persistence section, however the invoked script is named “w” instead of “u” and it was hosted on a different C2 URL, however the code was identical and produced matching file hashes.

Figure 17: Persistence – Scheduled Tasks“

Paessler PRTG fixes OpenSSL vulnerability CVE-2022-1292

Paesslers PRTG version 22.3.79 will update its internal OpenSSL libraries to 1.0.2ze in order to address and fix CVE-2022-1292. CVE-2022-1292 is categorized as CWE-78 (Improper Neutralization of Special Elements used in an OS Command 'OS Command Injection').

PRTG release notes of version 22.3.79:
[Security] We updated our OpenSSL libraries to version 1.0.2ze that patches CVE-2022-1292.

CVE-2022-1292 is about the OpenSSL c_rehash script, which does not properly sanitise shell metacharacters to prevent command injection.

Citrix ICA SSO saved credentials in XOR obfuscated readable storage

The Citrix ICA application stores user credentials for its SingleSignOn SSO functionality in readable form using XOR obfuscation with the key „C“, as Benjam Delpy wrote:

Mimikatz version 3 will be able to reveal this as shown in the following GIF with Windows 11 and Credential Guard enabled:

Quick win securing Azure AD

An easy quick win for securing Azure Active Directory passwords is the feature "Azure AD Password Protection". This helps you in mitre att&cks tactic credential access, for example in the technique brute force and its sub-techniques password guessing, password spraying, credential stuffing, etc.

Users are recommended to avoide simple passwords and instead should use pass-sentences. Password breaches of the recent past reveal that the majority still chose simple passwords. Azure AD Password Protection finds (audit mode) or enforces (enforce mode) stronger passwords for everybody. There is a hidden global banned password list which is applied to every user in the Azure AD tenant. Additionally you can block custom words like your companys name, your companys slogan, the founders or CEOs name, most used childerens names or your country or famous sport team names, which are often used as weak passwords.

Azure AD security custom banned passwords

Microsoft promises the "password validation algorithm" automatically detects/blocks variants and combinations like "password!1", "!password", "p@ssw0rd" and so on.

This is also available for on-premise Active Directory using an agent:

On-Premise Active Directory security quick win


However this needs an additional license, you need to install and agent on your domain controllers, you need to reboot the domain controllers and you need Azure AD. Also you do not see the changing content of Microsofts global password list and there is no enforcement based on Active Directory groups or OUs, so you for example cant just enforce it to priviledged accounts but must enforce it for everybody.

Of course I highly recommend to use Multi Factor Authentication MFA everywhere.

Almost perfect protection for websites and other services - Mutual TLS

Its hard to secure your IT services and applications. The list of possible attacks is long, as shown in the Mitre Att&ck framework , the...