Is Someone Spying on My Computer? How to Check Network Connections on Windows

If your PC is behaving strangely — unusual network activity, unfamiliar processes, slow speeds with no obvious cause — it’s natural to wonder whether something is sending data from your computer without your knowledge. Here’s how to find out definitively, using built-in Windows tools and a free dedicated network monitor.

Signs Your Computer May Be Monitored or Compromised

Network-based spying or unwanted data collection often shows these symptoms:

• Unexplained network activity — your network light is blinking when you’re not actively using any app
• Slow internet despite nothing running — something may be consuming bandwidth in the background
• Unfamiliar processes in Task Manager — processes with names you don’t recognize
• PC randomly wakes from sleep — some tools wake the PC to phone home at scheduled intervals
• Antivirus alerts you dismissed — worth revisiting with a network check

The most reliable way to investigate is to look directly at what your PC is actually connecting to — not just what’s running, but what’s actively communicating over the network.

Method 1: Check Connections With netstat (Built-In)

Windows includes netstat, a command-line tool that shows all active network connections without any download required.

How to use it:

1. Press Windows + S, type cmd
2. Right-click Command Prompt → Run as administrator
3. Type the following and press Enter:

netstat -b

Each entry shows: local address and port, remote address and port, connection state, and the process name in brackets below it. Useful variants:

• netstat -ano — connections with PID numbers (cross-reference with Task Manager)
• netstat -b 5 — refreshes every 5 seconds for near-continuous monitoring

Limitations of netstat:

• Static snapshot — does not update in real time
• Text-heavy output, difficult to scan quickly
• No ability to block connections from within the tool

Method 2: Real-Time Monitoring With SterJo NetStalker

SterJo NetStalker is a free Windows network monitor that gives you a live, continuously updated view of every network connection on your PC — with process names, remote addresses, connection states, and one-click blocking, all in a readable interface.

Step-by-Step:

1. Download SterJo NetStalker — free, installer or portable
2. Right-click → Run as administrator — required for full process visibility
3. The connection list loads immediately showing all active TCP and UDP connections
4. For each connection you see: process name and full path, local and remote address with port, connection state, and PID
5. Right-click any suspicious entry to search Google for the process name
6. To block a program permanently, right-click → create block rule, or use the Policy Rules tab

What to Look For — Normal vs. Suspicious

Not every unfamiliar connection is malicious. Here’s how to read what you see:

How to investigate an unknown process:

1. Right-click in NetStalker → Search Google — opens a browser search for the exact process name
2. Check the full path shown — legitimate Windows processes are in C:\Windows\System32\ or C:\Program Files\. Processes in AppData\Temp or random directories are a red flag
3. Look up the remote IP at ipinfo.io to see which company/country it belongs to

How to Block a Suspicious Program

Option 1: Block via SterJo NetStalker (easiest)

1. Right-click the connection in NetStalker
2. Choose to create a block rule
3. The rule is added to the Policy Rules tab — the program is blocked from making network connections while NetStalker is running

Option 2: Block via Windows Firewall (system-level, persists always)

1. Search Windows Defender Firewall with Advanced Security
2. Click Outbound Rules → New Rule
3. Choose Program → browse to the executable path
4. Choose Block the connection → apply to all profiles → name and save

Other Checks: Startup Programs and Task Manager

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