Why It's Open

Port 7680 is used by Windows Delivery Optimization (WDO), a feature in Windows 10 and 11 that allows devices to share updates and Microsoft Store apps via peer-to-peer (P2P) networking. It’s typically open on Windows clients and sometimes on Windows Server if Delivery Optimization is enabled. This service helps reduce bandwidth usage by retrieving updates from local or internet peers instead of downloading everything directly from Microsoft.

Common Risks

While intended to improve efficiency, leaving port 7680 open—especially to public networks—can introduce several risks:

NTP Amplification Attacks: Used in DDoS attacks. A small request from an attacker leads to a large response from the NTP server, overwhelming a target.
Information Disclosure: Misconfigured NTP servers can leak version info, system uptime, and internal IPs.
Spoofing/Time Shifting: Manipulating NTP responses can desynchronize systems, breaking logs or authentication.

Enumeration & Testing

🔎 Check if it’s open

nmap -sT -p 7680 <target-ip>

🔎 Scan for Windows DO Service

nmap --script=banner -p 7680 <target-ip>

📡 Check traffic with netstat (on Windows)

netstat -an | findstr :7680

Known Exploits

CVE-2017-11829
An elevation of privilege vulnerability exists when Windows Update Delivery Optimization does not properly enforce file share permissions.
🔗 NVD Entry
🔗 Microsoft Advisory
CVE-2019-1289
An elevation of privilege vulnerability exists when Windows Update Delivery Optimization does not properly enforce file share permissions.
🔗 NVD Entry
🔗 Microsoft Advisory
CVE-2020-0983
An elevation of privilege vulnerability exists when the Windows Delivery Optimization service improperly handles objects in memory.
🔗 NVD Entry
🔗 Microsoft Advisory

What to Look For

Checkpoint	What it means
Port 7680 open externally	Device might be sharing updates with internet peers
High bandwidth usage	Could indicate excessive DO activity
No ACL/firewall in place	Risk of abuse from external entities
DO allowed on all networks	May share data beyond corporate/LAN boundaries

Mitigation

Block TCP/7680 on the perimeter firewall unless explicitly required.
Configure Group Policy to restrict Delivery Optimization:
- Open gpedit.msc
- Navigate to Computer Configuration > Administrative Templates > Windows Components > Delivery Optimization
- Enable and configure:
  - Download Mode: Use LAN or Group instead of Internet
  - Restrict Peer Selection: Ensure only internal peers are used

Disable Delivery Optimization if not needed:

Stop-Service DoSvc
Set-Service DoSvc -StartupType Disabled

Real World Example

In enterprise networks, misconfigured Delivery Optimization has led to excessive WAN usage, as branch office devices attempted to download updates from internet peers rather than using internal caches or WSUS. In some audit cases, 7680 was found exposed on public IPs, leaking behavioral metadata.

TL;DR

Port 7680 = Windows Delivery Optimization
Used for P2P update sharing
Should not be internet-facing
Control bandwidth, peer scope, and exposure
Harden via GPO and firewall rules