Ransomware Defense: Preventing, Detecting, and Recovering from Attacks

Ransomware attacks have evolved from opportunistic malware infections into sophisticated, multi-stage operations conducted by organized threat groups. Modern ransomware operators conduct weeks of reconnaissance, exfiltrate sensitive data before encryption, and leverage double extortion tactics—threatening to publish stolen data if ransom demands are not met. Organizations in Bangladesh are increasingly targeted as digital infrastructure expands. At Nexis Limited, we help companies build comprehensive ransomware resilience across prevention, detection, and recovery domains.

Prevention: Reducing the Attack Surface

Ransomware prevention starts with eliminating common entry points. Remote Desktop Protocol (RDP) exposed to the internet is the single most exploited vector—disable it or restrict access through VPN with MFA. Phishing emails carrying malicious attachments or links account for the second largest entry vector; deploy email security gateways with sandboxing capabilities and enforce DMARC policies. Patch management is non-negotiable: known vulnerabilities in VPN appliances (Fortinet, Pulse Secure), Microsoft Exchange, and web-facing applications are routinely exploited within days of disclosure. Automated patch management with a maximum 72-hour window for critical vulnerabilities should be the organizational standard.

Network Segmentation

Flat networks allow ransomware to propagate laterally across the entire infrastructure within minutes. Network segmentation isolates critical assets—databases, backup systems, domain controllers—into separate network zones with strict inter-zone firewall policies. SMB (port 445) and RPC traffic should be restricted between segments, as these protocols are commonly abused for lateral movement. Backup infrastructure must reside in an isolated segment with no inbound connectivity from the production network.

Detection: Identifying Ransomware Before Encryption

Modern Endpoint Detection and Response (EDR) platforms detect ransomware behavioral indicators before mass encryption begins. Key indicators include: rapid file enumeration across network shares, volume shadow copy deletion (vssadmin delete shadows), unusual process chains (e.g., Excel spawning PowerShell), and mass file rename operations. SIEM correlation rules should alert on these patterns, particularly when combined with other indicators like disabled antivirus services or new scheduled tasks created via command line. Honeypot files—decoy documents placed in common directories—provide high-fidelity detection signals when accessed or modified.

Backup Strategy: The Last Line of Defense

Backups are the ultimate ransomware recovery mechanism, but only if they survive the attack. Follow the 3-2-1-1 rule: three copies of data, on two different media types, with one copy offsite and one copy offline or immutable. Immutable backups—stored on write-once media or in object storage with object lock enabled—cannot be encrypted or deleted by ransomware operators even with administrative access. Test backup restoration regularly; a backup that cannot be restored is equivalent to no backup at all. Document Recovery Point Objectives (RPO) and Recovery Time Objectives (RTO) for each critical system to set realistic expectations.

Incident Response: When Ransomware Strikes

Despite best preventive efforts, organizations must prepare for the possibility of a successful ransomware attack. The immediate response priorities are containment and evidence preservation. Isolate affected systems from the network immediately—disable network interfaces, but do not power off systems, as volatile memory contains forensic evidence. Identify the ransomware variant using file extensions and ransom notes via resources like ID Ransomware. Engage incident response specialists and legal counsel before making any communication with threat actors. Report the incident to BD-CERT and relevant law enforcement agencies.

Recovery and Lessons Learned

Recovery involves rebuilding affected systems from clean images, restoring data from verified backups, and methodically bringing services back online starting with the most critical. Before reconnecting recovered systems, ensure the initial access vector has been identified and remediated—otherwise reinfection is likely. Post-incident, conduct a thorough lessons-learned review: what detection failed, how the attacker gained initial access, where segmentation gaps existed, and what process improvements are needed. This review directly feeds into updated prevention and detection capabilities.

Ransomware resilience is not a product you can purchase—it is an organizational capability built through systematic preparation. Every layer of defense you implement increases the cost and difficulty for attackers, making your organization a less attractive target. Contact us to assess your ransomware readiness and build a defense strategy tailored to your infrastructure.