Resilience Is the Key to a Successful Defensive Strategy

The main mission of any CISO is not to prevent breaches of their infrastructure, rather, it's to safeguard you organizations' sensitive data and identity. I've said many time in the past that there are no device breach notifications but there are plenty of data breach notification laws. There are many ways to protect data and identity like encryption, monitoring outbound traffic, increasing user awareness, multi-factor authentication. These are important things but they are a means to achieve a goal. Resilience is the key to a sound defensive strategy. Here are some thoughts.

1. We play defense not offense. 95% of companies hire cybersecurity people to defend their company from cyberattacks. They don't hire them to attack other sites. That's what the remaining 5% do. However, to play good defense, one must know how to play good offense. In other words, a Blue Team should have strong Red Team skills.
2. One must accept the fact that a breach will happen regardless of whatever controls are in place. The old defensive strategy of building a "wall" to keep the bad guys out has failed. While there are many variants of the now popular Zero Trust Network philosophy, there are 2 key points that must be in place:
1. The network is hostile.
2. Data and identity are the new borders
3. The key to a successful defensive strategy is resilience not prevention.  A sound resilience strategy is key to recovery.

Resilience 

I could give the Webster's dictionary definition of resilience but let me give you an example.

Ransomware is one of the destructive attacks that has affected a large number of organizations and people recently.  It's been around since 1989 but what made it popular was the introduction of cryptocurrency as the payment mechanism. For example, the Virginia State prescription monitoring database was hit with a ransomware attack in 2009 and the attackers demanded a $10M ransom. The state didn't pay and restored from backups. There was a disruption of service, some loss of data but the service recovered. Collecting the $10M in small bills requires a bunch of duffel bags and every LEO in the planet watching those bags to see who collects them. 

This incident convinced me that the best defense against ransomware attacks is not "prevention", rather, it is "recovery". Take the time to carefully align file permissions with need-to-access requirements of the business. This is a difficult step. It may limit ransomware damage by limiting the files the malware can access.

 

A good backup strategy is the best defense in this case. A system gets hit with ransomware, you wipe it, patch it, restore your data from good backups and then move on with your business. A good resilience strategy should include these steps:

• find your sensitive data. Consolidate it into something like a data lake. 
• Map where your sensitive data goes within your network borders as well as outside your borders. 
• Backup this data lake by taking snapshots, doing old school incremental backups and store the backups offline in a read-only mode. For example, NetApp devices allow the creation of a read-only snapshot.
• Test your recovery processes frequently.

The old RFC 1244 "Site Security Handbook" describes two defensive strategies: "Protect and Proceed" and "Pursue and Prosecute".  It set the following conditions for each of these approaches:

 

Protect and Proceed

      1. If assets are not well protected.

      2. If continued penetration could result in great

         financial risk.

      3. If the possibility or willingness to prosecute

         is not present.

      4. If user base is unknown.

      5. If users are unsophisticated and their work is

         vulnerable.

      6. If the site is vulnerable to lawsuits from users, e.g.,

         if their resources are undermined.

   Pursue and Prosecute

      1. If assets and systems are well protected.

      2. If good backups are available.

      3. If the risk to the assets is outweighed by the

         disruption caused by the present and possibly future

         penetrations.

      4. If this is a concentrated attack occurring with great

         frequency and intensity.

      5. If the site has a natural attraction to intruders, and

         consequently regularly attracts intruders.

      6. If the site is willing to incur the financial (or other)

         risk to assets by allowing the penetrator continue.

      7. If intruder access can be controlled.

      8. If the monitoring tools are sufficiently well-developed

         to make the pursuit worthwhile.

      9. If the support staff is sufficiently clever and knowledgable

         about the operating system, related utilities, and systems

         to make the pursuit worthwhile.

      10. If there is willingness on the part of management to

          prosecute.

                                             Figure 1. Protect and Proceed vs Pursue and Prosecute

My ransomware scenario's recovery process is an implementation of requirement listed in RFC 1244 - " "Attempts will be made to actively interfere with the intruder's processes, prevent further access and begin immediate damage assessment and recovery." 

This is an example of resilience. Andy Greenberg's book "Sandworm" has a chapter dedicated to resilience. Dan Geer's essay "A Rubicon" is another example of the importance of resilience. Creating an "parallel" network universe addresses interdependency issues and allows for a quick recovery.

We should certainly spend funds on detection tools but the bulk of present-day defenses should be focused on how we recover from an attack. Resilience processes such as backups,  monitoring and disrupting outbound traffic to questionable sites are examples of a good resilience strategy. 

You're going to get breached at some point in time. How fast you recover can limit the damage done to your business processes. 

References

https://assets.documentcloud.org/documents/4366740/Geer-Webready-Updated.pdf

https://tools.ietf.org/html/rfc1244

https://mysupport.netapp.com/NOW/public/eseries/sam_archive1150/index.html#page/GUID-8538272A-B802-49D9-9EA2-96C82DAD26A2/GUID-F6C0C512-F196-4008-97AE-EA06EE4D32F6.html