Tag Archives: User Awareness

How to defeat antivirus evasion and privilege escalation techniques

4 February 2018

Last weekend I read two very informative posts on Antivirus Evasion by Mattia Campagnano. But part 2 [1] puzzled me somewhat.

“Following up to my previous post Tips for an Information Security Analyst/Pentester career – Ep. 43: AV Evasion (pt. 1), we’re going now to perform the same attack on a genuine Windows 10 machine, where all latest updates have been installed.”

For a moment I thought ‘a security professional mistakes compliance for security’ because ‘fully patched’ means not that the system is resilient against cyber-attacks. But both posts show that even the most secure Windows ever is vulnerable against privilege escalation and AV evasion if the basic configuration is not changed and fundamental elements of cyber hygiene are missing.

Why are such attacks successful?

First, the user was logged in with permanent administrative privileges. This makes life easy for attackers and fosters lateral movement.

Revoking permanent administrative privileges on workstations and servers must be a basic element of any cyber security program. Under normal conditions, standard users should not have any administrative privileges for their devices at all. If needed, they can be temporarily granted through User Account Control (UAC).

Second, UAC was not set to the highest level “Always notify me”. Unfortunately this is the standard setting after a fresh installation of Windows. With this, privilege escalation is possible without user notification. If configured properly, UAC will notify the user even if he works with administrative privileges.

The BypassUAC method in the meterpreter attack framework will fail, if UAC is set to the highest level. The following excerpt of the code [2] makes this clear

case get_uac_level
 when UAC_PROMPT_CREDS_IF_SECURE_DESKTOP,
      UAC_PROMPT_CONSENT_IF_SECURE_DESKTOP,
      UAC_PROMPT_CREDS, UAC_PROMPT_CONSENT
 fail_with(Failure::NotVulnerable,
  "UAC is set to 'Always Notify'. This module does not bypass this setting, exiting..."
 )
 when UAC_DEFAULT
    print_good('UAC is set to Default')
    print_good('BypassUAC can bypass this setting, continuing...')
 when UAC_NO_PROMPT
    print_warning('UAC set to DoNotPrompt - using ShellExecute "runas" method instead')
    shell_execute_exe
  return
end

Standards like the DISA STIG for Windows 10 [3] activate all UAC features to make life for the attackers as difficult as possible. From my point of view, the STIGs should be considered also in industry to create workplaces resilient against cyber-attacks. And Microsoft should raise the Windows default for UAC to “Always notify me” for all versions. If a user wants to reduce the security level, he should do this on his own responsibility.

Besides the secure configuration of IT systems and cyber hygiene is user awareness training the third essential pillar of a security program. Users and help desk staff must take proper actions if their system unexpectedly enters the secure desktop and asks for permissions of an action they never asked.

Have a good weekend.


  1. Campagnano, M. Tips for an Information Security Analyst/Pentester career – Ep. 44: AV Evasion (pt 2). The S@vvy_Geek Tips Tech Blog
  2. Rapid7 bypassuac_vbs.rb  Metasploit Framework. (Accessed: 3rd February 2018)
  3. Windows 10 Security Technical Implementation Guide. STIG Viewer | Unified Compliance Framework® Available at: https://www.stigviewer.com/stig/windows_10/. (Accessed: 3rd February 2018)
  4. Campagnano, M. Tips for an Information Security Analyst/Pentester career – Ep. 43: AV Evasion (pt.1). The S@vvy_Geek Tips Tech Blog
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Webinar Digital Extortion: Will you pay the ransom?

27 July 2016

I attended the IBM Security Webinar “Digital Extortion: Will you pay the ransom?” this evening. Limor Kessem talked about the history of and the latest trends in ransomware. Robert Lelewski provides an overview of the means to guard against and to recover from ransomware attacks.

Robert Lelewski showed a really remarkable slide:

Train users to beware of threats

Train users to beware of threats

The message is simple: Your users are the first line of defense. User training is the most effective means of combating cyber-attacks.

For more details, see the IBM ransomware landing page.

Have a good day.

Don’t ‘Enable Macro if you can’t read the entire document’!

9 April 2016

Since some weeks so-called file-less malware is experiencing a new boom. File-less malware is used in cyber-attacks for some years now. New is, that no executable is downloaded from a C&C server. Once the Trojan has become persistent it downloads a PowerShell script from the C&C server and uses PowerShell for encrypting the victim’s files.

PowerShell gives the attacker access to the Windows cryptographic functions. In this case, the AES standard is used. For more details, please see this analysis on malwr.com.

Actually, this is nothing new. Even the delivery method, in this case a spear phishing attack with a Word document, is well-known. And in the case that editing is deactivated for security reasons, the attacker provides concise instructions for activation:

PowerWare Ransomware Instructions to disable Macro Security

PowerWare Ransomware Instructions to disable Macro Security. Picture Credits: Carbonblack.com

The great challenge is to keep user awareness high. Hopefully this will prevent users to go ahead as follows:

Have a good weekend.

Some thoughts on ‘Dridex Reminds Us: You Can’t Prevent What You Can’t Detect’

28 March 2015

The latest Bromium post is really worth reading. Dridex is a further development of the Cridex Trojan. Dridex’s only goal is to steal your online banking credentials, to allow cyber-criminals to empty your bank accounts.

Dridex is a real beast. The developers hide the payload in Microsoft Office AutoClose macros to lever out the protection through the inbuilt sandboxing technology. If properly configured protected mode is a challenging task, but the bad guys had taken even this into account.

Michael Mimoso writes on threat post: ‘While macros are disabled by default since the release of Office 2007, the malware includes somewhat convincing social engineering that urges the user to enable macros—with directions included—in order to view an important invoice, bill or other sensitive document.’

The first line of defense, user awareness, has failed spectacularly! If someone tries to persuade you to disable protected mode for viewing an email attachment, it is very likely that this is a cyber-attack.

Task virtualization would have protected the user in this case. But even the task virtualization has its limitations. From my point of view, well-trained users, who are aware of the dangers of the internet, are the first line of defense today. Technology supports them to stay secure

… unless the users deactivates or the attackers bypasses them.

Have a good weekend.