Cyber Threat Report: 'Bringing Access Back — Initial Access Brokers Exploit F5 BIG-IP (CVE-2023-46747) and ScreenConnect'

This blog post by researchers at Mandiant describes how the threat actor UNC5174 exploited vulnerabilities in F5 BIG-IP appliances and Connectwise ScreenConnect, affecting numerous institutions, primarily in the U.S. and Canada. UNC5174 is believed to be a former Chinese hacktivist now acting as a contractor for China's Ministry of State Security, focusing on access operations. Researchers observed intrusions against Southeast Asian and U.S. research and education institutions, Hong Kong businesses, NGOs, and U.S. and UK government organizations. The post includes Indicators of Compromise (IOCs), MITRE ATT&CK techniques and remediation / hardening recommendations.

Application Isolation and Sandboxing

Restrict execution of code to a virtual environment on or in transit to an endpoint system.

Exploit Protection

Use capabilities to detect and block conditions that may lead to or be indicative of a software exploit occurring.

Vulnerability Scanning

Vulnerability scanning is used to find potentially exploitable software vulnerabilities to remediate them.

Privileged Account Management

Manage the creation, modification, use, and permissions associated to privileged accounts, including SYSTEM and root.

Update Software

Perform regular software updates to mitigate exploitation risk.

Network Segmentation

Architect sections of the network to isolate critical systems, functions, or resources. Use physical and logical segmentation to prevent access to potentially sensitive systems and information. Use a DMZ to contain any internet-facing services...

Filter Network Traffic

Use network appliances to filter ingress or egress traffic and perform protocol-based filtering. Configure software on endpoints to filter network traffic.

Network Intrusion Prevention

Use intrusion detection signatures to block traffic at network boundaries.

Execution Prevention

Block execution of code on a system through application control, and/or script blocking.

Restrict File and Directory Permissions

Restrict access by setting directory and file permissions that are not specific to users or privileged accounts.

Credential Access Protection

Use capabilities to prevent successful credential access by adversaries; including blocking forms of credential dumping.

Boot Integrity

Use secure methods to boot a system and verify the integrity of the operating system and loading mechanisms.

Code Signing

Enforce binary and application integrity with digital signature verification to prevent untrusted code from executing.

Multi-factor Authentication

Use two or more pieces of evidence to authenticate to a system; such as username and password in addition to a token from a physical smart card or token generator.

Password Policies

Set and enforce secure password policies for accounts.

SSL/TLS Inspection

Break and inspect SSL/TLS sessions to look at encrypted web traffic for adversary activity.

Antivirus/Antimalware

Use signatures or heuristics to detect malicious software.

Restrict Web-Based Content

Restrict use of certain websites, block downloads/attachments, block Javascript, restrict browser extensions, etc.

Disable or Remove Feature or Program

Remove or deny access to unnecessary and potentially vulnerable software to prevent abuse by adversaries.

Behavior Prevention on Endpoint

Use capabilities to prevent suspicious behavior patterns from occurring on endpoint systems. This could include suspicious process, file, API call, etc. behavior.

Audit

Perform audits or scans of systems, permissions, insecure software, insecure configurations, etc. to identify potential weaknesses.

User Training

Train users to be aware of access or manipulation attempts by an adversary to reduce the risk of successful spearphishing, social engineering, and other techniques that involve user interaction.

Pre-compromise

This category is used for any applicable mitigation activities that apply to techniques occurring before an adversary gains Initial Access, such as Reconnaissance and Resource Development techniques.