How the Chinese took, and lost, control at TechNet

happygeek 1 417 Views

While keen to point out that Microsoft's TechNet portal security was "in no way compromised" by the tactic, researchers with security outfit FireEye discovered that had managed to create profiles and posts on TechNet that contained embedded Command and Control codes for use with a BlackCoffee malware variant.

This method of hiding in plain sight is nothing new, but it can make detection problematical as the data (especially within a technical forum such as TechNet) is simply 'lost' in a sea of similar code from genuine users of a well respected and therefore assumed to be safe site.

The technique may, however, have backfired having been detected. The FireEye researchers have been working with the Microsoft Threat Intelligence Center to inject their own data onto some of those TechNet pages and use this to gain insight into how the malware, and the people behind it, operate. Ultimately, this will make both identification of infected forum systems and the cleansing thereof much easier.

Tim Erlin, Director of Product Management at Tripwire, warns that while using a legitimate website to distribute malicious data is nothing new "the addition of obfuscation here is a twist that makes detection just that much harder" and points out that "any website that allows for public comments to be submitted is already monitoring for abuse, but they can only detect what they’re actually looking for. Now that this technique has been surfaced, website administrators will adapt to identify it, and the criminals will have to shift again to avoid detection."

Dani AI

Generated

As summarized, the core trick was hiding command-and-control material inside otherwise normal forum content so signature-only defenses miss it. Below are practical, low-friction controls and triage steps that remain useful for public technical forums long after a single incident.

Simple detection heuristics (can be run on new posts)

  • Flag long contiguous base64-like strings and repeated hex-escaped bytes; these are common C2 carriers.
  • Measure string entropy and flag unusually high-entropy tokens inside posts.
  • Correlate flags with account age, posting cadence and IP reputation to reduce noise.

Example quick detector (toy Python sketch — tune thresholds and whitelists before use):

import math, collections, re

def entropy(s):
    cnt = collections.Counter(s)
    p = [c/len(s) for c in cnt.values()]
    return -sum(x*math.log2(x) for x in p)

b64_re = re.compile(r'\b[A-Za-z0-9+/]{40,}={0,2}\b')
hex_re = re.compile(r'(?:\\x[0-9A-Fa-f]{2}){8,}')

def find_suspicious(text):
    for m in b64_re.finditer(text):
        s = m.group(0)
        if entropy(s) > 4.5:
            return ('base64', s)
    if hex_re.search(text):
        return ('hex', hex_re.search(text).group(0))
    return None

Operational mitigations and triage workflow

  • Require moderation or extra review for first N posts from new accounts; throttle raw HTML/script posting.
  • Enforce code-blocks with language tags; strip or neutralize inline scripts and unknown tags.
  • When a post is flagged: decode payload offline in a sandbox, extract indicators (domains, IPs), and correlate with DNS, proxy and EDR logs for periodic polling. If a host is implicated, collect volatile data, isolate and preserve images for forensics.
  • Keep automated takedown + notification steps ready to remove malicious posts while preserving copies for investigation.

Caveats

  • Base64 and hex appear legitimately in many code examples and attachments — tune length/entropy thresholds and maintain a whitelist for common examples (images, certs, snippets). Maintain retention of raw logs for 30–90 days to support retrospective correlation.
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