Ransomware gangs target an organization's data to encrypt, rendering it unavailable and attempting to restore it. The threat is evolving, and recent tactics include theft of an organization's data accompanied by threats to release it to competitors or the public in an attempt to up the stakes and force a company to comply with the blackmail. Attacks are increasing in number and cost per incident. According to IBM, a single successful ransomware attack can cost up to $60 Million 1, and demands are frequently in the tens of millions of dollars 2. Trends have shifted to attacks against large corporations that can afford substantial settlements. Still, attention may go back to more minor victims if they manage to wrangle in their cyber-security en masse. No matter what size of your organization, now is the time to develop a strong threat response.
A thorough approach to Ransomware prevention, detection, and response includes preventing initial access, having strong access controls on network endpoints, developing early detection capabilities for identifying active malware, and mitigating the worst-case scenario by developing and maintaining effective backup strategies. First, let us briefly examine the stages of a ransomware attack and then focus on the last line of defense to prevent the worst-case scenario - adequate backups.
The initial steps of launching a Ransomware cyber-attack are identical to other types of Malware attacks but distinguish themselves in the latter stages. The critical steps to a successful Ransomware attack pattern go something like this:
Because the initial steps of launching a Ransomware cyber-attack are identical to other types of cyber-attack, strong best practices for reducing the attack surface should be applied to all endpoints. Some industry-leading organizations, including NIST and CISA, have published detailed advisories for preventing initial access and enabling early detection of Ransomware attacks 24. However, the latter stages of a Ransomware attack are distinct from other types of cyber-attack and deserve special attention. Restoring from back-ups is a last-line of defense that can determine a Ransomware attack's ultimate success in forcing an organization to pay to regain access.
Having reliable push-button recovery from stored backups can enable recovery of critical systems and files and potentially avoid millions of dollars of ransom payout. However, industry advisories specifically aimed at Ransomware backup strategy are numerous and provide a mountain of information regarding backup best practices, planning, implementation, and technical options 579. At the same time, additional industry best-practice advisories should also be consulted when building a robust backup strategy 1012. Therefore, let us envision backups as a last line of defense by extracting the most critical elements from those industry advisories.
Data comes in many shapes and sizes, embodying a variety of business continuity risks. Identifying and labeling data allows prioritization and application of risk management. However, carefully documenting and labeling all types of data according to their sensitivity level and operational criticality must happen before making decisions about particular technical solutions. Some of the most critical data include authentication passwords and keys, email correspondence, customer data, financial records, system event logs, sensitive business documents such as R&D project data, user documents, custom applications, and many other types of data depending on the individual organization.
Backup options themselves also come in several types.
The 3-2-1 backup strategy model advises keeping three copies of data on at least two types of media with one last-resort Backup in the cloud or otherwise stored offsite. However, a rethink of the time-honored 3-2-1 strategy has been proposed advising variations in line with specific organizational risk appetite 14. An example of a variation of the traditional 3-2-1 would be a 3-2-2, which may include one copy stored in the cloud and one copy air-gapped and held off-site.
If backups are on network storage, accessible Ransomware attacks have in the past and will continue to attack backups. Air-gapping full backups for critical systems is the most effective way to ensure safe data. Rotating backups keeping only one copy functional at any given time increases security by providing only one copy is reliably protected. Some large enterprises have responded by deploying offline tape-backups as a strategy. However, tape backups are expensive and require specialized IT staff, making it difficult for most SMEs.
Whether air-gapped or not, backup data needs to be further protected using additional measures. Even for air-gapped backups, note that network-attached storage devices contain their embedded operating system that could become infected with malware. Therefore, any backups with network access should employ strict access controls to protect the data from unauthorized access.
Completed backup data stores should have write permissions disabled for all users, including the data owner. This provides an additional measure of protection from unauthorized encryption. In addition, self-encrypting drives can protect the most sensitive data if physical backup drives are stolen. Finally, the integrity of each critical Backup should be validated periodically by taking hash-sums of the contents.
Ensuring the effectiveness of a backup solution requires testing to verify that restoration can happen reliably and as soon as possible. This testing process is necessary for determining the actual operational ability to meet RPO objectives and allows a chance to optimize and improve the restoration process. Table-top exercises are meetings where all critical staff discuss their roles in a restoration. Functional exercises prepare staff to identify gaps in planned procedures and validate procedural effectiveness.
An effective strategy to protect an organization against Ransomware includes prevention and response planning. The best-case scenario is preventing initial access with solid perimeter defenses. Stringent access controls can limit the extent to which Ransomware can pivot and impact critical resources. In addition, early detection strategies may be able to identify and stop exploitation at an early stage by containing and eradicating the Ransomware tools before they can infect and encrypt data. However, a failure to prevent these initial stages allows only a single last line of defense - backups.
Since Ransomware and Malware strategies and payloads are constantly evolving, developing and deploying a bullet-proof backup system as a last line of defense is critical. A backup plan can be designed to limit the amount of loss and recovery time based on the sensitivity level of various types of data in an organization while optimizing costs. Cloud and air-gapped backups are a crucial component of an effective backup strategy to keep a barrier between persistent Ransomware and data, and testing backups periodically ensure their integrity. Finally, table-top and functional exercises help prepare for the worst-case Ransomware scenario.