⚠️ Overview

CockBlocker is a relatively obscure ransomware strain first documented in April 2018 by security researchers at MalwareHunterTeam. It belongs to the ransomware category, designed primarily to encrypt files on infected Windows systems and demand a ransom for decryption. The malware’s operator or origin remains publicly unverified, but its distribution was primarily through malicious email attachments and exploit kits.

🔧 Technical Capabilities

CockBlocker employs AES-256 encryption to lock user files, appending a custom extension to affected filenames. Propagation occurs via phishing emails with booby‑trapped Office documents and drive‑by downloads from compromised websites. The ransomware communicates with its command‑and‑control (C2) infrastructure over HTTP to exfiltrate system information and receive encryption keys. Persistence is achieved by creating a scheduled task under the user’s profile and writing registry run keys under HKCUSoftwareMicrosoftWindowsCurrentVersionRun. Evasion includes checking for sandbox environments by querying the system’s BIOS and disk size, and it terminates processes that might interfere with encryption, such as shadow copy services.

📜 History & Notable Incidents

The first known sample of CockBlocker was uploaded to VirusTotal in April 2018, with low detection rates at the time. No major high‑profile victims or law enforcement actions have been publicly linked to this strain. It did not exploit any documented CVEs but relied on social engineering via the Trickbot botnet’s malspam campaigns for initial access. The malware was observed sporadically through mid‑2018, then largely faded from active distribution.

🔍 Detection Indicators

Known file hashes include the SHA‑256 value e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 (as reported by MalwareHunterTeam). Behavioral indicators include the creation of a ransom note named cockblocker.hta in each encrypted directory, network connections to IP addresses on port 8080, and the mutex name GlobalCockBlock_Mutex. Registry keys added under HKCU...Run point to a randomly named executable in the user’s AppData folder.

☠️ Risk & Impact

Encrypted files are rendered inaccessible unless victims pay a ransom—typically demanded in Bitcoin—though no public cases of decryption key recovery have been verified. The impact is primarily financial, targeting individual consumers and small businesses, with no confirmed data exfiltration beyond system profiling. Due to low prevalence, the overall risk is considered minimal compared to major ransomware families.

🛡️ Mitigation

Defensive measures include blocking common attachment types in email gateways, applying Microsoft Office macro security policies, and maintaining offline backups. Endpoint detection solutions should monitor for the cockblocker.hta file creation and the mutex string. No formal patches exist; mitigation relies on user awareness and updated anti‑malware signatures.

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