Tag Archives: SMB

Why is the industry such vulnerable against WannaCry and NotPetya style attacks? Part II.

16 July 2017

In part one of this post I discussed the impact of the aging IT infrastructure on the industry’s vulnerability against WannaCry and NotPetya style attacks. Part II deals with the OS basics.

Built-in features of the Windows operating system

Windows is the hacker’s paradise. Not because of the endless stream of vulnerabilities. I my opinion, Microsoft does a good job in managing this.

But because Windows is designed to support the efficient administration of networks with thousands of windows workstations, servers, users and applications.

The authorization subsystem (Active Directory) allows the assignment of fine grained permissions to users and groups to whatever resources, and the authorization check before access to resources in near real-time. It is highly scalable to support a single office LAN as well as a segmented global network.

Built-in utilities like Admin Shares, WMI (Windows Management Instrumentation), netsh, ipconfig, and the net command enable administrators to query and to change workstation, server and user settings across the network and to support efficient software distribution and troubleshooting. Windows Server Update Service (WSUS) supports the administrators in keeping the known vulnerabilities patched.

Everything is of course scriptable with the Windows Command Shell, Powershell and VBScript. All utilities can be leveraged up to a certain extent by every user and fully by administrators.

And of course, also by malware or cyber-criminals. Once a cyber-criminal managed to get on your network with e.g. a RAT (Remote Access Toolkit), he can walk across your network and do his malicious work with just the built-in tools. A download of utilities from a C&C (command and Control) server is not necessary. With this, the cyber-criminal is nearly invisible and he will stay nearly invisible for a long time if he makes no errors.

The Principle of least privilege is implemented in Windows at all levels of the OS stack. This is ensured by the Secure Development Lifecycle (SDL), which is the mandatory Microsoft development policy since 2004. Thus, under normal conditions, the Windows built-in security features would limit the impact of a malware.

Unfortunately, software failures cannot be avoided by the SDL because they are systemic errors – we build them during development right into the software. Once a process state triggers such a systemic error and someone finds a method to reproduce the error condition, the error becomes a vulnerability, e.g. MS017-10. This is no problem unless an exploit is published which allows a cyber-criminal to leverage the vulnerability for e.g. privilege escalation. With this, he gets full access to all the built-in tools and to all processes, including the authorization subsystem.

But even if exploiting a vulnerability leads not to a privilege escalation only some patience is needed. Just probe the network until a user is found who works with permanent administrative privileges. If such a session is hijacked, a cyber-criminal gets full access to all tools and the authorization subsystem on the computer.

With administrative privileges the attacker or malware can dump the authorization subsystem on the computer and extract either the password hashes or the clear text passwords. The example below shows an extract created by MIMIKATZ on a Windows 7 Enterprise Editon Workstation.

C:\Program Files (x86)\mimikatz\x64>mimikatz
.#####.   mimikatz 2.1.1 (x64) built on Jun 18 2017 18:46:28
.## ^ ##.  "A La Vie, A L'Amour"
## / \ ##  /* * *
## \ / ##   Benjamin DELPY `gentilkiwi` ( benjamin@gentilkiwi.com )
'## v ##'   http://blog.gentilkiwi.com/mimikatz             (oe.eo)
'#####'                                     with 21 modules * * */
....

Authentication Id : 0 ; 315690 (00000000:0004d12a)
Session           : Interactive from 1
User Name         : kjochem
Domain            : WIN-2OLSA000OLM
Logon Server      : WIN-2OLSA000OLM
Logon Time        : 16.07.2017 21:31:24
SID               : S-1-5-21-3248755352-2707638487-1840279341-1000
msv :
[00000003] Primary
* Username : kjochem
* Domain   : WIN-2OLSA000OLM
* NTLM     : dd94b116548a739e24ad775193c2d13b <--- Password hash
    ….. 
wdigest :
* Username : kjochem
* Domain   : WIN-2OLSA000OLM
* Password : #Not very12strange! <--- Clear text password
kerberos :
* Username : kjochem
* Domain   : WIN-2OLSA000OLM
* Password : (null)
ssp :
credman :

The extracted passwords can be used for direct login to further systems, the password hashes in Pass-the-Hash attacks on further nodes. In any case the chance of detection is low since the attacker behaves like a normal user.

This is the way NotPetya works and other malware worked in the past and will work in future.

Windows is highly optimized to allow cost effective operation of networks of thousands of computers. This leads automatically to misconfigurations, e.g. through domain based technical accounts with high privileges on all workstations and servers. In combination with users working with permanent administrative privileges the cyber criminal’s life is simplified.

What are mitigating measures?

The selection below makes no claim to be complete.

Migration to Windows 10.

Drop all old-style transportation and authentication protocols during this process. Migration to Windows 10 is the first choice because baseline security in Windows 10 is higher than in Windows 7. For example, the issue with the plain text passwords in the authorization subsystem is gone. But this is not helpful in industry because we must deal for at least 5 to 10 years with Windows 7 or Windows 2008 server and old-style protocols.

Short and mid-term mitigation measures.

  • Reduce the number of users working with permanent administrative rights to zero. This is a leadership task!
  • Implement priority patching of critical systems, especially for those on the perimeter to the production networks.
  • Review all firewall rules. Focus on required connections, limit the use of the SMB protocol as far as possible.
  • Review all technical users. Limit their functionality to the local systems and lowest possible privileges, if possible.
  • Roll out a security incident detection tool (SIEM) to all clients and servers. For example, dumping of processes in memory of a workstation or server is a clear indicator for a hacking attempt. Immediate action upon such events is required.
  • Implement privileged account and session management, in the best case with one-time passwords which are changed after the session ends.
  • Apply the measures to mitigate Pass-the-Hash attacks to all Windows networks. For details please see https://www.microsoft.com/en-us/download/details.aspx?id=36036.

Long-term measures.

  • Microsoft should build a production friendly Windows with limited functionality. This Windows should have a much smaller attack surface than the standard multi-purpose Windows systems of today.
  • The dependency on the SMB protocol for exchange of data between the office and the production networks should be reduced, in the best case to zero.

Have a great week!

Some thoughts on “Ransomware a real risk for SCADA networks”

5 June 2017

“By now the ‘Air gapping’ myth should be expunged from every ICS/SCADA manager on earth.” I really like this statement from Daniel Cohen-Sason, published on 23 May 2017 in the CYBERBIT blog.

From my point of view, the ‘Air Gap’ era ended with the introduction of portable engineering stations about 30 years ago.

Modern OT networks are often designed on the basis of the ISA 95 Standard with network zones and security devices, e.g. firewalls, to control the communications flow between the process control and SCADA systems across the zones. Modern production requires a lot of Machine-to-Machine (M2M) communication between the production networks zones and between the production network and the business network. Besides this M2M communication Human-to-Machine (H2M) communication is required, e.g. for operator access from the business network and for remote maintenance.

For M2M and H2M interaction communication channels must be opened on the firewalls. With this, there is always a chance that malware can spread across such required connections. Furthermore, cyber attackers can gain access, e.g. through remotely exploitable vulnerabilities, after they hijacked a M2M communications endpoint in the business network. We dealt with this very effectively in the past 20 years.

Many of the required connections use the SMB protocol for exchange of data. That’s no problem per se. The problem is, that we still use Windows 7 and Windows Server 2008 in the manufacturing industry which cannot work with the latest versions of the SMB protocol for data exchange.

Since WannaCry exploited a vulnerability in SMB version 1.0, it was only a matter of time before WannaCry would find its way across a required connection from the business network to the production network.

How to deal with the problem?

  • Priority patching.

The systems at the border between the business network and the production network must me patched with highest priority. Although this is somewhat tricky to achieve in WSUS, it’s worth to deal with this WSUS feature. In addition to the operating system components, all application components must be patched as well. The same applies to Linux based systems.

  • Deactivating SMB.

Is a great means in the case of an emergency, and part of a long-term data exchange strategy.

  • Set up asset and vulnerability management.

At least all systems at the endpoints of required M2M and H2M connections must be included. This enables you to evaluate the scale of the problem in the case of a new vulnerability.

  • Faster innovation cycles.

At least for the systems at the perimeter of the production network we must allow for shorter innovation cycles. With Windows 8, Windows 10, and Windows Server 2012, new versions of the SMB protocol are used which are not affected by WannaCry. Don’t forget to deactivate the SMB V1.0 compatibility in the this versions.

This includes the technology used for data exchange. For example, the widely used Robocopy fosters the spreading of WannaCry because it is based on the SMB protocol.

  • Increase the level of isolation.

Start with challenging the required M2M and H2M connections. Eliminate every connection without a business purpose. For the remaining, check whether the best available security technology is used.

Take care!

Why should companies migrate to Windows 10?

28 January 2015

This question is often asked in the media. Most companies shy away from migrating to Windows 8.1. One reason for this might be because they invested a considerable effort in the migration from Windows XP to Windows 7 only few years before.

Besides great security features like User Access Control, Microsoft introduced the SMB v2 protocol with Windows Vista. SMB v2 allows signing of network packets, which protects against Man-in-the-Middle attacks.

SMB v3 was introduced with Windows 8 and Windows Server 2012. SMB v3 allows encryption of data while it is transferred across the network, which protects against wiretapping.

In addition to SMB signing and encryption, Two Factor authentication will be introduced in Windows 10. Even if this security features would be the only innovations in Windows 10 (the new user interface looks great), I would strongly recommend companies to start the evaluation of Windows 10 as soon as possible.

Watch this YouTube video and form your opinion…

Don’t Panic!