Shahid Roofi Khan

Technologies Blog

Ransomware - Why end up paying ransom when you can timely protect yourself

Rise Of Ransomware

The rise of bitcoin and digital currencies have certainly opened the door to new challenge, bad guys have a way to make you pay them. Your vulnerable systems and infrastructure can now allow others to blackmail you. Even worse, once they are able to attack you, you can't simply get rid them of them, even worse, the vulnerabilities they tap, are not something you can fix in days, so most often you are totally helpless. This is one benefit of cloud infrastructure that you don't have to worry about its security but still your laptops and desktops and data that resides on them is always your responsibility.

How To Protect

The best defense is only possible when you have some idea of how is the attack possible. When you click on the URL links, from the internet or on the emails that you receive, you hackers the chance to get into your world. Those links seems legit and might open up and look normal but under the hood something malicious is planned. They make you download something which when you execute, you machine is then totally under the control of someone else. So your laptops and desktops on which users and checking emails and doing web browsers are the main sources or origin points from which this malicious things starts its working.

Your first and foremost, wish and priority at then, would be to stop this from spreading out to all rest of machines in your network and even worse, the servers that contains all the important data of all the users. So how does the spread happens. Normally when you want to copy any file to remote PC, in case of windows machines (which are mostly the target of this ransomwares) you need SMB protocol that open share folders on other machines, you need network path enabled between them and you need credentials to access the machine. In 2017, WannaCry Ransomware tapped the vulnerability present in SMB version 1 itself, which caused it to open the share folders of other machines even without passwords, which lead to lot of damage and then followed by patch from Microsoft which can totally block SMB version 1 from the client machine as well as server essentially blocking capability of windows machines to talk to each other on this vulnerable version of the protocol.

So your first defense of course is have proper patching in place and ensure old version of SMB i-e SMB 1.0 is totally blocked properly in your network. But is that enough to stop the spread? definitely not at all. Remember we discussed, all you need to reach out to other machine, is SMB protocol, network access and credentials and that's how it need work. Now lets suppose you are logged into a windows machine as administrator account which is common account to administer more than one machine, then obviously your current logged in credentials are sufficient to let the thing spread. So obviously in order to protect you need to follow the principle of least privileges which says, you should use least privileges to get the job done. So let's suppose you need to administer just the file servers, then have an administrator account specific to file servers and don't use super accounts like domain admins. In fact all those common accounts with access to almost all infrastructure should be super safe and used only and only when necessary. Same applies to common administrator account passwords. Suppose you have all desktops with the administrator account password same and let's suppose you are logged into one of them with admin ID, and its also makes the spread super simple. So you need to ensure there is no commonality across the machines in terms of credentials. There are many solutions like Microsoft free Solution name "LAPS" which rotates the local admin password on schedule.

Your next important step need to be segmentation on network level. Remember we discussed, the need to spread requires, network path also enabled. So let's suppose desktop is able to connect to every other desktop in the network, than that's a problem. Normally there is no need for desktops to talk to each other. Mostly these servers are talking to servers which is the end point of these desktops. But good network administration means, you segment you network. Particularly the ports that are used for SMB communication that help transfer of files to other machines, (normally port 445) need to be blocked from network. That is one smart thing that you can do in advance. You can also extend the idea to implement the org wide policy to let not PCs copies file from each other rather they are able to use only a file server for that purpose. Same idea can be extended to servers. Not all servers need to have SMB communicated required to every other servers. So high level of segmentation is very important here. Atleast one dept. of PCs should be totally blocked from reaching to other dept PCs. For server also, do extensive segmentation especially for this type of communication.

I recall doing security assessment for one Organization, they were using common credentials for all database servers service account which had domain admin privileges also. That surely is call to disaster. Because then these accounts you can't even change them easily. Changing the password for such an account is not easy also, because you have to break so many things that are already tied to that password. So that Org had to be in fix even after disaster for long.

Implement a good backup strategy and ensure that backups are kept on different type of technology. For example if you have tasks scheduled that backs up data on file servers and let's support file server is compromised, what good would be that backup for you? the backup files would be another useless data for you. Dedicated attached storage to backup solution / servers which is not shared directly on same network is type of thing you should look for. Especially the communication between backup solution and rest of infrastructure should be planned in a way that backup and restore can continue to function.

So to put together use below to prevent,

  • Make sure Windows and all software are up to date at any time. Regularly patch your machines(servers and desktops) and Isolate obsolete and unpatched machines at network level.
  • Credentials you have to plan them well. Remove all common accounts from common usage. Segment the accounts. Consider implementing the "Local Administrator Password Solution" (LAPS), if your local administrator account has the same password on all client machines: https://www.microsoft.com/en-us/download/details.aspx?id=46899 
  • Ensure weak SMB 1.0 protocol is properly blocked and ensure later SMB protocols v2/v3 are also properly blocked on the network wherever file sharing is not required between machines. 
  • Consider implementing MFA for all admin accounts (although MFA does not block the spread, but its good security measure to not let bad guys in).
  • Consider using Microsoft Advanced Threat Analytics:  https://docs.microsoft.com/en-us/advanced-threat-analytics/what-is-ata  (already in list above)
  • Monitor your firewalls (at boundaries and internal subnets) to identify machines generating suspicious traffic, like network scans, enumeration requests, or even exploit code usage. (to be addressed by relevant team). Consider enabling windows firewalls.
  • Make sure relevant log retention is in place on your proxy/firewall.
  • Backup your security audit logs and increase their sizes so you can later do forensics. Consider a centralized security logging solution.
  • Train your users (spear-phishing, Social Engineering), (like share this blog post with them).
  • Use the antivirus which provides best ransomware protection. Some even offer free decryptors for common and new ransomware attacks.
  • Backup Strategy, need to be planned well in advance for such situation in mind

So the best defense is of course possible with prevention. Doing all above is not possible at nick of time when you are already under attack.

There are certain things you should do, once you already affected,

  • Disconnect infected machines.
  • Reset twice compromised account passwords.
  • Reset twice local admin passwords especially if passwords are used on several machines to avoid lateral movements. 
  • Reset twice the password of privileged accounts in the domain (including service accounts).
  • Kerbtgt account password reset can be done for mitigation and monitoring purpose (do not forget to reset it twice) but it has to be planned preferably with a Microsoft experts/Vendors like us.
  • Schedule a full AV scan on your machines.
  • Please confirm that your local admin passwords are different and can’t be used to do lateral movement (LAPS usage). (local admin password need to be changed manually and on case basis before bring server on network). (Please consult with us if you need deployment of such solution)
  • Consider re-installing client machines used to administer any type of servers. 
  • Conduct a complete investigation and Incident response on the whole eco system.
  • Run vulnerability assessment scans and audits on all Internet-facing systems. 
  • Make sure all Windows security updates are installed (not only service packs).
  • Make sure all software is up to date. 
  • Check Exchange rules that are configured on user accounts, especially for high ranking executives. (to block internal executables transfer from exchange)
  • Monitor your firewalls (at boundaries and internal subnets) to identify machines generating suspicious traffic. 
  • On your Proxy/firewall make sure relevant log retention is in place. 
  • Increase event logs size– see https://technet.microsoft.com/en-us/library/cc748849(v=ws.11).aspx.

I hope this helps other timely to prevent such from happening and guide those already in such situation. Definitely much less can be done once such has already happened but yes lot of things can be done beforehand to prevent bad thing from happening in first place. Feel free to connect with us timely so we can help fill up the gap if any.

 

Comments (1) -

  • Jubail

    10/17/2020 3:27:10 PM | Reply

    cool. it is helpful. planning the same. maybe we need help on LAPs will contact you then.

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