HEAT: THE THREAT YOU DIDN’T SEE COMING
Imagine this: your SME has invested in next-gen firewalls, email gateways, and an EDR (Endpoint Detection and Response) solution that claims to catch even the stealthiest malware. Your employees are trained on phishing simulations, and you believe you’ve built a fortress.
Then, one morning, a senior employee receives an email from what appears to be a trusted partner—the email links to a Google Drive file containing a password-protected ZIP. Because your email security solution cannot inspect the contents, it sails through. The user downloads it, thinking it’s part of a routine business process. What happens next is invisible to your tools: the malicious payload is assembled in the browser through HTML smuggling. Sensitive data is silently exfiltrated, credentials are harvested, and by the time your security team notices unusual network activity, the damage is done.
This is the new reality of Highly Evasive Adaptive Threats (HEAT), a class of cyberattacks specifically designed to evade traditional detection methods. For SMEs, which often lack dedicated security operations centres, these attacks represent a silent but devastating risk.
WHAT MAKES HEAT DIFFERENT AND DANGEROUS
Unlike traditional attacks that rely on static malware or known malicious URLs, HEAT campaigns are living, morphing entities. They adapt to your defences, sidestep your controls, and use your users as the final execution point. Here are some of the primary tools in their arsenal:
| HEAT Technique | Why It Evades Defences | Real-World Example |
| Password-Protected Files | Security solutions can’t inspect encrypted attachments, so malicious payloads pass through unchecked. | Earth Preta, a state-backed group, distributed backdoors via password-protected archives hosted on Google Drive and Dropbox, bypassing enterprise email filters. |
| LURE (Legacy URL Reputation Evasion) | Attackers exploit URLs with good or aged reputations to sneak past URL filtering. | Phishing campaigns leveraging Google Ads directed users to fake login portals with excellent reputation scores, defeating automated filters. |
| HTML Smuggling | Payload is split into benign fragments that reassemble in the victim’s browser, invisible to traditional scanning. | Campaigns impersonating Adobe, Google, and USPS delivered Qakbot, IcedID, and Cobalt Strike payloads using this technique. |
| SEO Poisoning & Obfuscated JS | Legitimate-looking search results hide malicious scripts, and obfuscation keeps them hidden until runtime. | Gootloader campaigns targeting healthcare and legal sectors used poisoned search results and staged JS to deliver remote access Trojans (RATs). |
| MFA Bypass | Even MFA can be undermined by phishing pages that capture credentials and session cookies. | Reddit suffered a breach where attackers mimicked its intranet login page, captured credentials, and bypassed MFA protections. |
WHEN “GOOD ENOUGH SECURITY ISN’T ENOUGH
Many SMEs operate under the assumption that a layered defence, including email filtering, firewalls, endpoint security, and user training, is sufficient. Unfortunately, HEAT attacks exploit the gaps between these layers:
- Browser as a Blind Spot – Most endpoint tools focus on file-based threats but do little against browser-based attacks. If the malicious code executes in the browser, there’s often no visibility.
- Trusted Cloud Services as a Delivery Mechanism – Attackers use Google Drive, OneDrive, or Dropbox, knowing that most businesses whitelist these services to avoid blocking productivity.
- User Trust as a Weapon – HEAT attacks exploit human behaviour, delivering links and files that appear business-critical or time-sensitive.
SMEs often lack the resources for 24/7 SOC monitoring or threat hunting, making them prime targets for these stealthy campaigns.
SME CASE STUDIES: THE REAL-WORLD COST
- Healthcare Provider Breach: A mid-sized healthcare provider searching for policy templates stumbled onto an SEO-poisoned site that appeared on the first page of search results. The downloaded document was actually a malicious payload that installed a backdoor. Attackers gained access to patient records and the provider faced regulatory penalties, lawsuits, and months of reputational damage.
- Tech Startup Data Theft: A 100-person SaaS company received phishing emails that looked like internal Slack notifications. The links pointed to Dropbox-hosted password-protected ZIPs containing malicious JavaScript that executed in the browser via HTML smuggling. By the time the company discovered the breach, source code repositories had been cloned, leading to stolen IP and delayed funding.
These aren’t hypotheticals—they’re examples of what is already happening across industries.
WHAT SMES CAN DO: PRACTICAL DEFENCES AGAINST HEAT
Protecting against HEAT requires rethinking the security perimeter. Here’s a practical roadmap:
- Harden the Browser Environment
- Deploy Remote Browser Isolation (RBI) so that risky content is executed in a disposable cloud environment, not on endpoints.
- Consider secure enterprise browsers with built-in phishing and form-field inspection to stop credential harvesting.
- Deep Content Inspection
- Inspect password-protected files in a controlled sandbox before delivering to users.
- Use tools that analyse scripts at runtime to detect HTML smuggling and obfuscated JavaScript.
- Adaptive Policy Enforcement
- Enforce read-only modes on unknown sites.
- Block login forms on suspicious or uncategorized domains until they are verified.
- Behavioural Monitoring
- Watch for anomalies like users entering credentials on domains they never accessed before.
- Monitor unusual MFA prompt behaviour and flag out-of-band approval attempts.
- Incident Readiness
- SMEs must plan for post-breach scenarios, with playbooks to isolate devices, revoke credentials, and communicate transparently with customers.
BOTTOM LINE: THE NEW BATTLEFIELD FOR SMES
HEAT attacks shift the battlefield from the network perimeter to the browser session, where most modern work happens. SMEs that assume traditional defences are sufficient will increasingly find themselves blindsided.
Cybercriminals are shapeshifters. They evolve faster than static defences can keep up. But SMEs don’t have to be easy prey. By isolating browser activity, inspecting content dynamically, enforcing adaptive policies, and preparing for worst-case scenarios, they can make themselves a far harder target.
In the age of HEAT, survival isn’t about building taller walls; it’s about making attackers waste their time, fail fast, and move on to an easier victim.
PROTECT IT BETTER
As London’s #1 end-to-end cybersecurity and IT support for SMEs, Zhero knows the ins and outs of cyberattacks and how to mitigate these. Our Protect IT Better offering has been carefully crafted and developed to proactively nurture and build a sustainable cybersecurity environment giving your business a competitive advantage. We’ve incorporated the most advanced technology-as-a-service innovations and created Protect IT better. Protect IT better follows a holistic approach that ensures you are always protected against modern-day cyberattacks. Get in touch today to secure your world. Together we can make our online world in the UK and beyond safe for everybody.
