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CISO Briefing: Hackers Are Using ‘Teams’ Ads & Weaponized ‘PuTTY’ to Bypass EDR and Gain Full Network Access — by CyberDudeBivash

By CyberDudeBivash · 01 Nov 2025 · cyberdudebivash.com · Intel on cyberbivash.blogspot.com

LinkedIn: ThreatWirecryptobivash.code.blog

APT • EDR BYPASS • DLL SIDELOADING • TEAMS ATTACK

Situation: A new, high-sophistication attack is targeting your *most trusted* platforms. APTs (Advanced Persistent Threats) are using malvertising *inside Microsoft Teams* and search engines to lure sysadmins into downloading a *Trojanized “PuTTY”*. This attack uses DLL Sideloading to bypass your EDR and gain persistent, `SYSTEM`-level access.

This is a decision-grade CISO brief. This is a “trusted-on-trusted” attack (Teams + PuTTY) that *will* bypass your automated defenses. Your EDR is blind. Your SEG is blind. This is the new TTP for corporate espionage and ransomware deployment, and your SOC is likely to miss the “noise” until it’s too late.

TL;DR — Attackers are using malicious ads in Teams to push a fake “PuTTY” that bypasses EDR.

• The Lure: Malicious ads *inside* Microsoft Teams (or Google) for “PuTTY Download.”
• The TTP: DLL Sideloading. The ZIP contains a *legitimate, signed* `putty.exe` and a *malicious* DLL.
• The EDR Bypass: Your EDR sees a *trusted, signed* `putty.exe` process start and *ignores* it. The malicious DLL is loaded *in-memory* by this trusted process.
• The Impact: Ransomware, Corporate Espionage, and full Domain Admin compromise.
• THE ACTION: 1) HARDEN: Block EXEs from running in `Downloads/Temp` (use WDAC/AppLocker). 2) HUNT: This is the mandate. Hunt for anomalous `putty.exe` (or other admin tools) running from non-standard paths or making network connections.

TTP Factbox: “Trusted Process” DLL Sideloading

TTP	Component	Severity	Exploitability	Mitigation
DLL Sideloading (T1574.002)	`putty.exe` (or any signed EXE)	Critical	Bypasses EDR/AV Whitelisting	AppLocker / WDAC / MDR

Critical RCEEDR Bypass TTPLiving off the Land (LotL)

Risk: This TTP is a “Trusted Process” bypass. Your EDR is *designed* to trust `putty.exe`, making it *blind* to the malicious C2 beacon running in its memory.Contents

1. Phase 1: The “Trusted Platform” Lure (Malvertising in Teams)
2. Phase 2: The “Trusted Executable” TTP (DLL Sideloading)
3. Exploit Chain (Engineering)
4. Reproduction & Lab Setup (Safe)
5. Detection & Hunting Playbook
6. Mitigation & Hardening
7. Patch Validation (Blue-Team)
8. Tools We Recommend (Partner Links)
9. CyberDudeBivash Services & Apps
10. FAQ
11. Timeline & Credits
12. References

Phase 1: The “Trusted Platform” Lure (Malvertising in Teams)

As a CISO, your Secure Email Gateway (SEG) is hardened. Your employees are *trained* to distrust “Urgent Invoice.zip” from an external email.

Attackers know this. They have moved to a “trusted” platform: Microsoft Teams.

Your employees *trust* Teams implicitly. It’s their internal workspace. Attackers are now using malicious advertising (malvertising) *within* the Teams ad ecosystem, or simply poisoning Google/Bing search results that employees click on *while in* Teams.

The lure is targeted at *your most privileged users*:

• “Download the new PuTTY client”
• “Get the latest WinSCP”
• “Download this ‘missing’ codec to view this video”

A sysadmin or developer, trying to do their job, searches for “PuTTY” and clicks the first ad. This ad links to a *malicious* site (`putty-official-download.com`) that delivers a `.ZIP` file. The attack has bypassed your email security entirely and is now on the endpoint.

Service Note: This is an Initial Access TTP that blends Phishing and Social Engineering. Your *only* automated defense is an AI-powered tool that can spot this new wave of “trusted” phishing. This is why we built PhishRadar AI.
Explore PhishRadar AI by CyberDudeBivash →

Phase 2: The “Trusted Executable” TTP (DLL Sideloading)

This is where the EDR Bypass occurs. The user opens the downloaded `putty.zip`. Inside, they see two files:

1. `putty.exe` (This is the *real, legitimate, signed* executable from the official PuTTY developers. Its hash is clean.)
2. `version.dll` (This is the *attacker’s malicious backdoor*.)

When the user double-clicks `putty.exe`, Windows *follows a specific search order* to load its required DLLs. The *first* place it looks is the *application’s own directory*.

The legitimate `putty.exe` *is* vulnerable to this. It tries to load `version.dll`. Windows finds the *malicious* `version.dll` (in the same folder) *before* it finds the *real* one in `C:\Windows\System32`.

The attacker’s code (the C2 beacon) is now *loaded into the memory of `putty.exe`*.

Your EDR sees `putty.exe` (a *trusted, signed* process) start. It *whitelists* it.
Your Firewall sees `putty.exe` (a *known SSH client*) making an *outbound network connection*. This is *normal, expected behavior*.

Your entire security stack is blind. The attacker is in. This is a classic “Living off the Trusted Land” (LotL) attack.

Exploit Chain (Engineering)

This is a TTP, not a software CVE. The “exploit” is a *logic flaw* in the Windows loader path and the *assumptions* of your EDR.

• Trigger: User clicks `putty.exe` inside a folder containing a malicious DLL.
• Precondition: Attacker has placed *both* a vulnerable, signed EXE (`putty.exe`) and a malicious DLL (`version.dll`) in the same user-writable directory (`C:\Downloads\`).
• Sink (The RCE): The Windows Loader maps `putty.exe` into memory. It resolves dependencies. It searches for `version.dll` in the *local directory first*. It finds the *malicious* DLL, maps it into the *trusted* process’s memory, and calls its `DllMain`.
• Module/Build: `putty.exe` (Legit) → `version.dll` (Malicious C2 Implant).
• Patch Delta: There is no “patch.” The “fix” is Application Control (WDAC) to *prevent* this behavior.

Reproduction & Lab Setup (Safe)

You can *and should* test your EDR’s visibility for this TTP.

• Harness/Target: A sandboxed Windows 11 VM with your standard EDR agent installed.
• Test: 1) Create a “malicious” `version.dll` that simply spawns `calc.exe` (`CreateProcessW`). 2) Download a *legitimate, signed* `putty.exe`. 3) Place *both* in `C:\Temp\`.
• Execution: Double-click `putty.exe`.
• Result: Does PuTTY launch? And does `calc.exe` *also* launch? If “yes,” your EDR is *blind* to this TTP.
• Safety Note: NEVER use a real C2 payload. Use `calc.exe` as a *safe proof-of-concept*. If `calc.exe` can run, so can a Cobalt Strike beacon.

Detection & Hunting Playbook

Your SOC *must* hunt for this TTP. Your SIEM/EDR is blind to the exploit itself; it can *only* see the *result*. This is your playbook.

• Hunt TTP 1 (The #1 IOC): “Process running from non-standard path.” This is your P1 alert. `putty.exe` should *only* run from `C:\Program Files\`.# EDR / SIEM Hunt Query (Pseudocode) SELECT * FROM process_events WHERE (process_name = ‘putty.exe’ OR process_name = ‘vlc.exe’ OR process_name = ‘canon.exe’) AND (process_path NOT LIKE ‘C:\Program Files\%’ AND process_path NOT LIKE ‘C:\Windows\System32\%’)
• Hunt TTP 2 (The Child Process): “Why is `putty.exe` spawning `powershell.exe`?” A legit PuTTY session *never* does this. This is the *post-exploit* behavior.
• Hunt TTP 3 (The C2): “Why is `putty.exe` making a network connection to a *newly-registered domain* or *anomalous IP*?” This is the C2 beacon.

The “Noise” vs. “Signal”: Your automated EDR *will* miss this. It sees “trusted” processes. You *must* have a 24/7 human-led MDR team (like ours) that has the *context* to know that `putty.exe` running from `C:\Downloads\` is not “noise,” it’s a *critical breach*.
Explore Our 24/7 MDR Service →

Mitigation & Hardening

You cannot patch PuTTY to fix this (it’s a Windows “feature”). You must *harden the OS*.

• 1. Application Control (The *Real* Fix): This is your CISO mandate. Deploy Windows Defender Application Control (WDAC) or AppLocker. Create a GPO that blocks *all* executables (`.exe`, `.dll`) from running in user-writable paths (e.g., `C:\Users\*\Downloads`, `C:\Users\*\AppData\Local\Temp`). This *kills* this TTP.
• 2. Email Gateway Hardening: Block `.ZIP` files that *contain* `.LNK`, `.DLL`, or `.EXE` files.
• 3. EDR Tuning: Tune your Kaspersky EDR to *alert* on “Hunt TTP 1” (process from bad path) and “Hunt TTP 2” (anomalous child process).

Patch Validation (Blue-Team)

This is a TTP, not a CVE. There is *no patch*. The “validation” is *running a Red Team engagement*.

Your “Patch” is your Hardening Policy. Run the “Lab Setup” test (above) *after* you apply your new WDAC/AppLocker GPO.

# 1. Apply new GPO (Block EXEs from C:\Temp\)
# 2. Run gpupdate /force
# 3. Attempt to run C:\Temp\putty.exe
#
# EXPECTED RESULT:
# "This app has been blocked by your system administrator."
  

If you see this, your hardening is working. If `calc.exe` appears, you are *still vulnerable*.

Blue-Team Checklist:

• AUDIT: Run the “Hunt TTP 1” query *today* to see if you’re *already* breached.
• HARDEN: Deploy the WDAC/AppLocker GPO to *block* executables from user paths.
• HARDEN (Email): Block `.LNK` and `.DLL` files inside `.ZIP` attachments.
• HUNT: Create *new* SIEM/MDR alerts for the “Hunt TTPs” (anomalous paths, child processes, and network C2s).

Recommended by CyberDudeBivash (Partner Links)

You need a layered defense. Here’s our vetted stack for this specific threat.

Kaspersky EDR
This is your *sensor*. It’s the #1 tool for providing the behavioral telemetry (process chains, network data) that your *human* MDR team needs to hunt.Edureka — Threat Hunting Training
Your SOC team can’t find what they don’t know. Train them *now* on DLL Sideloading TTPs and LotL hunting.TurboVPN
Your *legitimate* admin access (RDP/SSH) should *only* be over a trusted, encrypted VPN, not the public internet.

Alibaba Cloud (VDI)
A key mitigation. Use Virtual Desktops (VDI). If the VDI is popped, you *burn it* and re-image in seconds. The host is safe.AliExpress (Hardware Keys)
*Mandate* this for all Domain Admins. Get FIDO2/YubiKey-compatible keys. They stop the *initial phish* from succeeding.Rewardful
Run a bug bounty program. Pay white-hats to find flaws *before* APTs do.

CyberDudeBivash Services & Apps

We don’t just report on these threats. We hunt them. We are the “human-in-the-loop” that your automated EDR is missing.

• Managed Detection & Response (MDR): This is the *solution*. Our 24/7 SOC team becomes your Threat Hunters, watching your EDR logs for these *exact* “DLL Sideloading” TTPs.
• Adversary Simulation (Red Team): This is the *proof*. We will simulate this *exact* EDR bypass kill chain to show you where you are blind.
• Emergency Incident Response (IR): You found this TTP? Call us. Our 24/7 team will hunt the attacker and eradicate them.
• PhishRadar AI — Stops the initial spear-phishing email that delivers the Stage 1 LNK foothold.
• SessionShield — Protects your *admin* sessions, so even if the attacker gets `SYSTEM`, we detect their anomalous *session* behavior.

Explore 24/7 MDR ServicesBook an Adversary Simulation (Red Team)Subscribe to ThreatWire

FAQ

Q: What is a LNK exploit?
A: It’s not a “vulnerability” in LNK files themselves, but a *technique*. It leverages a legitimate Windows function (shortcuts) to execute malicious code (like PowerShell) in a “fileless” way that evades simple antivirus.

Q: What is “DLL Sideloading”?
A: It’s an EDR bypass technique. An attacker “tricks” a *legitimate, signed* executable (like `putty.exe`) into loading a *malicious* DLL by placing it in the same folder. The EDR sees the “trusted” `.exe` and ignores it, while the malicious code runs in its memory.

Q: My EDR has “AI.” Am I safe?
A: No. Not automatically. Your AI is only as good as its configuration. If it’s configured to “trust all signed executables” (like `putty.exe`), it will *miss this*. This attack is designed to *exploit* that trust. You *must* have a *human* MDR team hunting for the *behavioral* anomalies.

Q: I found this TTP! What do I do?
A: 1. Isolate the host(s) immediately. 2. Do not turn it off (you will destroy the in-memory evidence). 3. Call our 24/7 Incident Response hotline. We need to perform memory forensics, find the persistence mechanism, and hunt for *lateral movement*.

Timeline & Credits

This “TTP Chaining” (Teams Malvertising -> LNK -> DLL Sideloading) is an active TTP observed by multiple threat intel groups, including CyberDudeBivash, as a primary vector for APTs like UNC6384 (China-nexus).

References

• MITRE ATT&CK: T1574.002 (DLL Sideloading)
• Microsoft: Living off the Land (LotL)
• CyberDudeBivash MDR Service

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