Nmap Crashing on Large Networks or with Certain Options on Kali Linux: Solutions and Workarounds

Nmap is a powerful network scanning tool that can be used to discover hosts and services on a network. However, it can sometimes crash when scanning large networks or when using certain options on Kali Linux.

There are a few reasons why Nmap might crash in these situations. One reason is that Nmap can use a lot of memory, especially when scanning large networks or using complex options. Another reason is that Nmap can sometimes encounter errors when communicating with remote hosts or firewalls.

In this article, we will examine some of the common causes of Nmap crashes on Kali Linux and provide some solutions and workarounds.

Common Causes of Nmap Crashes

Here are some of the most common causes of Nmap crashes on Kali Linux:

• Scanning large networks: Nmap can use a lot of memory when scanning large networks. If your system does not have enough memory, Nmap may crash.
• Using complex options: Some Nmap options, such as the -sC and -A options can be very resource-intensive. If you are using these options, you may need to increase the amount of memory allocated to Nmap.
• Encountering errors: Nmap can sometimes encounter errors when communicating with remote hosts or firewalls. These errors can cause Nmap to crash.

Solutions and Workarounds

Here are some solutions and workarounds for Nmap crashes on Kali Linux:

• Increase the amount of memory allocated to Nmap: You can increase the amount of memory allocated to Nmap by editing the /etc/nmap/nmap.conf file. Find the line that says max_scan_delay=0 and change it to max_scan_delay=300. This will tell Nmap to wait up to 300 seconds between sending probes. This will give your system more time to free up memory, which can help to prevent Nmap from crashing.
• Use simpler Nmap options: If you are using complex Nmap options, try using simpler options instead. For example, instead of using the -sC and -A options, you could use the -sS and -Pn options. These options are less resource-intensive and are less likely to cause Nmap to crash.
• Scan smaller networks: If you are scanning a large network, try scanning smaller networks instead. You can do this by using the -iL option to specify a list of networks to scan.
• Exclude certain hosts: If you are scanning a network that contains hosts that are causing Nmap to crash, you can exclude those hosts from the scan using the -e option.
• Use a different Nmap version: If you are still having problems with Nmap crashing, you can try using a different Nmap version. You can download different versions of Nmap from the Nmap website.

Example Codes

How to increase the amount of memory allocated to Nmap:

# Edit the /etc/nmap/nmap.conf file
sudo nano /etc/nmap/nmap.conf

# Find the line that says max_scan_delay=0 and change it to max_scan_delay=300
# Save the file and exit

# Restart Nmap
sudo service nmap restart

Scan a smaller network:

# Scan the 192.168.1.0/24 network
nmap -iL 192.168.1.0/24

How to exclude certain hosts from a scan:

# Scan the 192.168.1.0/24 network, excluding the host 192.168.1.100
nmap -iL 192.168.1.0/24 -e 192.168.1.100

The Bottom Line

Nmap is a powerful network scanning tool, but it can sometimes crash when scanning large networks or when using certain options on Kali Linux. The solutions and workarounds provided in this article should help you to prevent Nmap from crashing.