Understanding the Hosts File and Malware Relating to the Hosts File in Windows

Understanding the Hosts File and Malware Relating to the Hosts File in Windows - Printable Version

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Understanding the Hosts File and Malware Relating to the Hosts File in Windows - Sneakyone - 01-30-2025

Understanding the Hosts File and Malware Relating to the Hosts File in Windows

What is the Hosts File?
The **hosts file** in Windows is a system-level text file used to **map domain names to IP addresses** before the system queries a DNS server. It provides a way to override DNS resolution locally.

Default Hosts File Location in Windows:

Code:
C:\Windows\System32\drivers\etc\hosts

Example of a Default Windows Hosts File:

Code:
# This is a sample HOSTS file used by Microsoft TCP/IP.

# The IP address and the corresponding host name should be placed on individual lines.

127.0.0.1      localhost

::1            localhost

This file is used primarily for **network troubleshooting, local development, or blocking domains**.

How Does Malware Exploit the Hosts File?
Malware often **modifies the Windows hosts file** for malicious purposes, such as:

Redirecting users to **phishing or malicious websites**.
Blocking access to **antivirus/security update servers**.
Hijacking legitimate domain names to display **fake websites**.
Preventing users from visiting **security-related domains**.

Example of a Maliciously Modified Hosts File:

Code:
0.0.1      www.microsoft.com

0.0.1      www.google.com

0.113.50    www.bankwebsite.com  # Redirects to a phishing page

In this case, Microsoft and Google are **blocked**, while the banking website is **redirected** to a fraudulent server.

How to Check If Your Hosts File Is Compromised
To inspect the hosts file in Windows:

Press **Win + R**, type **notepad C:\Windows\System32\drivers\etc\hosts**, and press **Enter**.
If you see suspicious entries like **unknown IP addresses mapped to popular websites**, your hosts file may be infected.
Compare your hosts file with the default format (see above).

How to Restore the Default Hosts File in Windows

Method 1: Manually Reset the Hosts File

Open **Notepad as Administrator** (`Win + R`, type `notepad`, press **Ctrl + Shift + Enter**).
Click **File > Open**, navigate to:

Code:
C:\Windows\System32\drivers\etc
Change file type to **All Files** (`*. *`), then open **hosts**.
Delete any **suspicious or unknown entries**.
Save the file and restart your computer.

Method 2: Use Microsoft’s Official Hosts File Reset Tool

Visit **Microsoft's Support Page**.
Download the **Fix it** tool to reset the hosts file.

Method 3: Reset the Hosts File Using Command Prompt

Open **Command Prompt as Administrator** (`Win + R`, type `cmd`, press **Ctrl + Shift + Enter**).
Run the following command:

Code:
type nul > C:\Windows\System32\drivers\etc\hosts
Then restore the default hosts file with:

Code:
echo 127.0.0.1 localhost > C:\Windows\System32\drivers\etc\hosts
Restart your computer.

How to Protect the Hosts File from Malware

**Make the hosts file read-only** to prevent unauthorized modifications:

Code:
attrib +r C:\Windows\System32\drivers\etc\hosts
Use **antivirus software** that monitors changes to the hosts file.
Enable **Windows Defender’s Tamper Protection** to block modifications.
Avoid downloading **untrusted programs** that can alter system settings.
Regularly check the hosts file for **unexpected changes**.

Detecting and Removing Hosts File Malware
If malware keeps modifying your hosts file, use **anti-malware tools**:

**Malwarebytes** - Detects and removes hosts file infections.
**HitmanPro** - Scans for malware that modifies system files.
**ESET Online Scanner** - Free cloud-based malware scanner.
**Microsoft Safety Scanner** - Checks for system infections.
**Kaspersky TDSSKiller** - Detects rootkits that modify the hosts file.

If malware persists:

Boot into **Safe Mode** (`Win + R`, type `msconfig`, go to **Boot > Safe Mode**).
Run a **full antivirus scan**.
Reset the hosts file manually.

Conclusion

The **Windows hosts file** is a powerful tool for local DNS resolution.
Malware often **abuses the hosts file** to hijack web traffic or block security updates.
Regular **monitoring and security best practices** can help prevent modifications.
If the hosts file is compromised, **reset it and remove malware** immediately.

Keeping the hosts file secure is essential to preventing cyber threats and ensuring a safe browsing experience.

Code:
https://pastebin.com/tZvhBq2t