Tag Archives: Poweliks

How to defend against file-less malware?

15 July 2019

Stories on file-less malware are constantly appearing in the news. Zeljka Zorz’s post “A file-less campaign is dropping the Astaroth info-stealer” (1), published on 9 July 2019 in Help Net Security, gives a great introduction into the techniques used in file-less attacks.

Andrea Lelli’s technical analysis (2) shows that the malware downloads some DLLs and injects them into the userinit.exe process after becoming persistent. So, no big development since the first report on a file-less malware, Poweliks (3), published in 2014.

Pattern based anti-malware solutions are still no effective means to protect against file-less malware because the malware uses the hacker’s favorite toolkit, the Windows OS, for installation of the malicious payload.

But there is no reason to panic. The Windows OS is part of the problem; the Windows OS is also part of the solution.

First things first.

Don’t work with permanent administrative privileges!

It cannot be repeated often enough! Userinit.exe is part of the Windows OS. Admin privileges are required to load a DLL into the userinit.exe process. So, no admin rights, no DLL injection.

Now the big change.

We need change!

We need change!

In a Windows environment, Microsoft AppLocker does the job. AppLocker is an efficient solution; it is part of the Windows OS and it can be configured centrally by group policies. AppLocker is an effective solution; all kind of dropper malware is blocked, and with DLL rules enforced, DLL injection is no longer possible. Thus, AppLocker is the perfect solution for SMBs to overcome the shortcomings of pattern based anti-malware solutions. For a brief overview on AppLocker see my post (4).

If AppLocker does not fit into your computing environment, for example in production, look at the application whitelisting solutions from the big anti-malware solution providers. Application whitelisting provides additional features, e.g. the lockdown of systems, which is of interest especially in production because of the much longer solution lifecycles.

Application whitelisting is the long overdue change in the strategic approach to cyber security. Give it a try. Once you locked down your systems you can take care of the really important issues. Like supporting your business in digitalization initiatives.

Have a great week.


References

  1. Zorz Z. A fileless campaign is dropping the Astaroth info-stealer [Internet]. Help Net Security. 2019 [zitiert 15. Juli 2019]. Verfügbar unter: https://www.helpnetsecurity.com/2019/07/09/astaroth-fileless-malware/
  2. Lelli A. Dismantling a fileless campaign: Microsoft Defender ATP next-gen protection exposes Astaroth attack [Internet]. Microsoft Security. 2019 [zitiert 15. Juli 2019]. Verfügbar unter: https://www.microsoft.com/security/blog/2019/07/08/dismantling-a-fileless-campaign-microsoft-defender-atp-next-gen-protection-exposes-astaroth-attack/
  3. Jochem K. Review – ‘Poweliks’ malware variant employs new antivirus evasion techniques [Internet]. IT Security Matters. 2014 [zitiert 15. Juli 2019]. Verfügbar unter: https://klausjochem.me/2014/08/09/poweliks-malware-variant-employs-new-antivirus-evasion-techniques/
  4. Jochem K. Windows Applocker – The almost forgotten IT security workbench [Internet]. IT Security Matters. 2019 [zitiert 15. Juli 2019]. Verfügbar unter: https://klausjochem.me/2019/01/05/windows-applocker-the-almost-forgotten-it-security-workbench/
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AppGuard protection concepts II

19 June 2016

Preventing the execution of whatever scripts or executables from User Space is one of the basic security concepts of AppGuard. Unfortunately, the User Space concept does not work in the case of fileless malware. A very prominent representative of this malware type is Poweliks.  Poweliks was first detected in August 2014. It hides its payload in the Windows registry, no file is written during the first infection phase.

In the McAfee Labs Threats Report: November 2015 McAfee researchers described in detail how the fileless Kovter malware infects a victim’s system. Kovter writes JavaScript to the registry. This script calls an encrypted PowerShell Script which is also stored in the registry. Finally, the code is written to the memory of another process and executed within the context of this memory.

During this last write process AppGuard’s MemoryGuard enters the game:

Memory protection is designed to prevent one process (originator) from altering or reading the memory of another process (target). Attackers try to re-allocate memory, place executable code into the newly allocated memory, and then execute this code. This type of attack is known as memory code injection and memory scraping. This attack has been widely used in file-less malware which exists only in memory, and Trojan downloader type of malware.

Sound’s easy. Again, ProcessExplorer is the perfect means to show how MemoryGuard works:

Process Explorer: User Process Tree Unprotected

Process Explorer: User Process Tree Unprotected

Process Explorer: User Process Tree in Protected Mode

Process Explorer: User Process Tree in Protected Mode

In Protected mode icons and process descriptions are no longer displayed. Process Explorer retrieves these details from the process memory, and MemoryGuard blocks read access.

Process Explorer: Regedit Process Details Unprotected

Process Explorer: Process Details Unprotected

Process Explorer: Regedit Process Details Protected

Process Explorer: Process Details Protected

In Protected mode important process details are no longer displayed. Process Explorer reads these details from a process’ memory and displays them in the Properties dialogue. If AppGuard is operated in the default mode Protected, MemoryGuard blocks this reading operations, thus details about the process cannot be retrieved.

MemoryGuard is a really charming concept, and out-of-the-box available after installation.

Have a good weekend.

Software manufacturers have no sense for IT security – Part II

23 October 2014

Sometimes malware protection software works too well. I found some emails with malicious executables, disguised as pdf files, in the attachment in my junk-mail folder. Unfortunately the anti-malware system removed the attachments and replaced them by the filename.

Some weeks ago a new kind of malware that resides solely in the registry was in the news. To implant Poweliks attackers must exploit a vulnerability of the system and, the good faith of the users. Pdf or rtf documents with embedded malicious code are used very often to start the attack.

Just why is the Adobe Reader such a popular tool for attackers?

Adobe Reader is very popular for viewing of pdf documents, and very notorious for its vulnerabilities. The list of known vulnerabilities published in the National Vulnerability Database is really long, and some of them are perfectly suited to implant malware. By the way, Adobe Flash Player is as popular as the Adobe Reader for attackers, and the list of vulnerabilities is of comparable size.

Fortunately advanced security options like a sandbox are available to defend malicious attacks, but these are not activated during a standard installation. Even for enterprise users the standard installation procedure must be pre-configured.

I can’t find a reason why Adobe does not install the Reader with advanced security options enabled by default. Apparently, Adobe is not interested in protecting the privacy and security of their customers.

Fortunately the National Checklist Program Repository provides ‘detailed low level guidance on setting the security configuration of operating systems and applications’.

For Acrobat Reader X a checklist is available which could be easily adapted to the Acrobat Reader XI. Although this checklist is meant for pre-configuring installation packages the configuration hints could be used to secure existing installations as well:

Navigate to menu Edit/Preferences.

In category General section Application Startup activate option Use only certified plug-ins.

In category Security (Enhanced) set the protection options as described below:

Adobe ReaderEnhanced Security Settings

Adobe ReaderEnhanced Security Settings

[1] Enable sandboxing for all files

[2] Enable Enhanced Security

[3] Disable all Privileged Locations.

Although this sounds somewhat paranoid viewing of pdf files is much more secure now. A pdf file is now opened in a sandbox running at the lowest integrity level. Most features are disabled by default, but could be enabled with just one click.

Enjoy!

Poweliks it is still stuck in my mind

17 August 2014

It may sound funny, but Poweliks is still stuck in my mind. The bad news for me is: Poweliks resides only in Windows registry.

The good news is: To start at every login the malware uses the Windows registry, namely the outdated method of using the [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run] key.

And this is exactly the vulnerability of Poweliks we can use for taking counter measures!

The Windows policy ‘Do not process the legacy run list’ could be used to block Poweliks. If enabled this policy blocks the programs listed in the run key from getting executed during login. That’s it!

Do Not Process Legacy Run List Policy

Do Not Process Legacy Run List Policy

To enable the ‘Do not process the run once list’ policy start the local group policy editor gpedit.msc and navigate to section User Configuration\Administrative Templates\System\Logon. Double click the policy, select option ‘Enabled’, enter a comment and click ‘Apply’.

Use policy ‘Run these programs at user logon’ to whitelist the programs which you want to start at login. To prevent unwanted programs from getting started during system boot, enable the ‘Do not process the run once list’ in Computer Configuration as well.

Sounds somewhat strange, like fighting fire with fire. A much better solution would be to isolate all applications in AppContainers like Internet Explorer and run them at integrity level “Low” when connected to whatever network.

Microsoft, please do us this favour in Windows 10 the latest!

Review – ‘Poweliks’ malware variant employs new antivirus evasion techniques

9 August 2014

On 4 August 2014 Brandan Blevins talks in his post ‘‘Poweliks’ malware variant employs new antivirus evasion techniques‘ about a new malware which uses new infection routes.

My first thought was: Oh no, not another new malware that could not be detected by state-of-the-art Anti Virus systems!

My second thought was: Hold on for a moment. The Poweliks malware appears to jump into our computers like a deus ex machina! Sounds like magic, doesn’t it?

If you dig somewhat deeper, you find, that to implant the malware, attackers must exploit a vulnerability of the system and, the good faith of the users. In this case the media was a Word attachment of an email and a flaw in the MSCOMCTL.OCX described in CVE-2012-0158.

In section ‘What might an attacker use the vulnerability to do?’ Microsoft describes the impact:

Bacteriophage P2. Source: Mostafa Fatehi

Bacteriophage P2. Source: Mostafa Fatehi

‘An attacker who successfully exploited this vulnerability could gain the same user rights as the logged-on user. If a user is logged on with administrative user rights, an attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights…’.

And this is exactly what the Poweliks malware does.

What countermeasures could we take?

(a) Do not open attachment and files from untrusted sources like email. Common sense can prevent lots of malware attacks.

(b) Do not work with permanent administrative rights.

(c) Change the User Account Control (UAC) Settings to the highest level ‘Always notify’. The malware installs Powershell, if not already installed. In this case UAC will notify you.

(d) Check whether the latest updates and patches are installed. CVE-2012-0158 was fixed in 2012 and can not be used for an attack, if Windows Update is configured to automatically install updates.

(e) Review the Trust Center Settings in Microsoft Office.

Activate ‘ Disable all macros with notification’ in section ‘Macro Settings’,

Activate ‘Prompt me before enabling all controls with minimal restrictions’ in section ‘ActiveX Settings’.

Activate ‘File Block Settings’ except for Office 2007 or later formats in section ‘File Block Settings’.

(f) Check your AV providers Homepage for the latest updates or utilities. I bet you will find some Information or tool which could support you in an emergency.

(g) Don’t Panic!

Have a good Weekend