Over 30,000 New Attacking IP Addresses Hit Your Network Every Day

 

CRITICAL RDP Warning: Over 30,000 New Attacking IP Addresses Hit Your Network Every Day

By CyberDudeBivash • Updated Oct 21, 2025 • Apps & Services

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TL;DR 

1. RDP (TCP/3389) is hammered nonstop by botnets, credential-stuffers, and opportunistic scanners. New hostile IPs rotate in daily at Internet scale.
2. Never expose RDP directly to the Internet. Put it behind VPN/Zero-Trust, enforce MFA, and restrict by source (geo/IP).
3. Harden Windows: NLA on, strong lockout, disable weak crypto, randomize non-standard ports (still not a control), patch RDP stack.
4. Continuously block & rotate: Use dynamic IP intelligence (fail2ban/Windows Firewall/Intune) and auto-rotate deny lists.
5. Incident playbook below: live commands, event IDs, detection rules, and a printable IR checklist.

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Cloud & Cybersecurity courses (career boost) Kaspersky
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VPN entry for remote RDP (never expose 3389) ASUS India
Business laptops/servers with TPM & Secure Boot

Table of Contents

1. The RDP Reality: Why Your 3389 Is a Magnet
2. Attack Matrix: How RDP Is Abused
3. Golden Rule: No Direct Internet RDP
4. Harden Windows for RDP (Step-by-Step)
5. Network Controls (Firewall, Geo, WAF, ZTNA)
6. Detect & Respond: Event IDs, Queries, Alerts
7. Incident Response Checklist (Printable)
8. FAQs

The RDP Reality: Why Your 3389 Is a Magnet

Remote Desktop Protocol (RDP) remains one of the most targeted services on the public Internet. Botnets enumerate IPv4/IPv6 ranges continuously, harvest leaked credentials, and spray them against exposed endpoints. Even if you block thousands of IPs today, fresh sources appear tomorrow via new nodes, proxies, and cloud instances. Treat exposure as a certainty—not a possibility.

• Drivers: cheap initial access for ransomware, crypto-mining, data theft, and lateral movement.
• Rotation: hostile IPs churn rapidly; static blocklists age fast. Automate block/decay cycles.
• Deception: consider canary RDP banners or honeypots to collect IOC telemetry safely.

Attack Matrix: How RDP Is Abused

• Credential Stuffing: using breached passwords against domain/local accounts.
• Brute Force: high-rate sprays; low/slow to evade thresholds.
• Exploits: unpatched RDP vulnerabilities (historical CVEs) to bypass auth or cause DoS.
• Man-in-the-Middle: downgrade or TLS interception when configs are weak.
• Post-Auth: persistence via services, Run keys, RDP shadowing, disabled EDR, data staging.

Golden Rule: No Direct Internet RDP

Never publish TCP/3389 to the world. Preferred options:

1. Zero-Trust Network Access (ZTNA): device posture + user identity + per-app tunnels.
2. Site-to-Site / Client VPN: restrict to trusted source IPs; enforce MFA on VPN.
3. Jump Hosts / Bastion: hardened, audited, and isolated; no lateral Internet reach-back.
4. Just-In-Time Access: ephemeral grants for admins; auto-expire.

Harden Windows for RDP (Step-by-Step)

1) Turn On NLA + Strong Crypto

• System Properties → Remote → Allow Remote Assistance (off unless needed) → Allow Remote Connections with NLA required.
• Group Policy: Computer Config → Admin Templates → Windows Components → Remote Desktop Services → Remote Desktop Session Host → Security
  Enforce: Require user authentication for remote connections by using NLA, set Encryption level: High, disable legacy TLS/RC4.

2) MFA for RDP

• Integrate with smartcards, FIDO2, or vendor MFA that hooks RDP logon.
• For domain: enforce conditional policies via your IdP for VPN/ZTNA gates.

3) Account Policies & Lockout

• 5-10 invalid attempts → lockout 15-30 min; reset counter ≥ 30 min.
• Block built-in admin for network logon; use unique named admin with vault rotation.

4) Least Privilege & Session Limits

• Only required accounts in Remote Desktop Users group.
• Idle/session timeouts; deny local drive/clipboard redirect unless necessary.

5) Patch & Configuration Baselines

• Apply monthly OS and RDP stack updates promptly.
• Adopt CIS/Microsoft security baselines; verify drift with configuration scanning.

6) Rename Default Port (Defense-in-Depth)

Change port from 3389 to a random high port (obscurity only); combine with strict source rules. Do not rely on this as a control.

7) PowerShell Quick Checks

# Is RDP enabled?
(Get-ItemProperty 'HKLM:\System\CurrentControlSet\Control\Terminal Server').fDenyTSConnections

# NLA status (1=Required)
(Get-ItemProperty 'HKLM:\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp').UserAuthentication

# Current listeners
netstat -ano | findstr LISTENING | findstr :3389
  

Network Controls (Firewall, Geo, WAF, ZTNA)

• Windows Firewall: inbound allow only from admin bastion/VPN subnets; deny others by default.
• Edge Firewalls: geo-block regions irrelevant to operations; throttle new sources.
• Deny-List Automation: sinkhole repeat offenders; expire after 7-14 days to avoid list bloat.
• ZTNA/WAF: publish RDP via app gateways that enforce identity, device posture, and per-session audit.

Detect & Respond: Event IDs, Queries, Alerts

Key Windows Event IDs

• 4624/4625 Logon success/failure (pay attention to Type 10/3).
• 4776 NTLM auth attempts.
• 1149 (TerminalServices-RemoteConnectionManager) RDP auth success.
• 1024/1025 (TermService) RDP session connect/disconnect.

Sample PowerShell (Last 24h Failed RDP Logons)

Get-WinEvent -FilterHashtable @{LogName='Security'; Id=4625; StartTime=(Get-Date).AddDays(-1)} |
  Where-Object { $_.Properties[8].Value -eq 10 } |  # Logon Type 10 (RemoteInteractive)
  Select-Object TimeCreated, @{n='IpAddress';e={$_.Properties[19].Value}}, @{n='TargetUser';e={$_.Properties[5].Value}} |
  Sort-Object TimeCreated -Descending
  

SIEM Hunting (concepts)

• Aggregate failures by source / user / hour; alert on spikes or new ASN/geo.
• Correlate with threat-intel feeds (cloud, commercial, open-source).
• Detect RDP lateral movement: chained Type 10 logons between servers.

Incident Response Checklist (Printable)

1. Contain: Temporarily block inbound RDP at edge; enable only via bastion/VPN.
2. Triage: Pull last 7–30 days of 4624/4625/1149; isolate anomalous IPs/users/ASNs.
3. Credentials: Force password reset + MFA re-registration for targeted admins.
4. Persistence: Check new services, scheduled tasks, startup items, RDP shadow; validate EDR is active.
5. Hardening: Enforce NLA, lockout policy, and remove direct Internet exposure.
6. Monitor: 72-hour heightened logging + alerts; add deny-lists with timed expiry.
7. Review: Post-mortem; add ZTNA/JIT and improve detection thresholds.

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Monetize your security SaaS/consulting

Next Reads from CyberDudeBivash

• Windows Security (all posts)
• Network Defense & ZTNA Guides
• Daily Threat Intel

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FAQs

Is changing the RDP port enough?

No. It reduces noise but is not a security control. Combine with VPN/ZTNA, NLA, MFA, and strict allowlists.

Can I rely on IP blocklists?

Use them as a dynamic layer with expiry. Attack sources rotate quickly—pair with identity-aware access and strong auth.

What’s the safest way to provide remote access to admins?

Hardened bastion/jump host behind VPN or ZTNA with device posture checks, MFA, session recording, and JIT access.

#CyberDudeBivash #RDP #RemoteDesktop #BruteForce #CredentialStuffing #ZeroTrust #WindowsSecurity #BlueTeam #SOC #ZTNA #VPN #ThreatIntel