ZMap – The Internet Scanner

ZMap is an open source single packet network scanner designed for Internet-wide network surveys. On a typical desktop computer with a gigabit Ethernet connection, ZMap is capable scanning the entire public IPv4 address space in under 45 minutes.

With a 10gigE connection and PF_RING, ZMap can scan the IPv4 address space in under 5 minutes. It operates on GNU/Linux, Mac OS, and BSD. It currently has fully implemented probe modules for TCP SYN scans, ICMP, DNS queries, UPnP, BACNET, and can send a large number of UDP probes.

Since ZMap is designed to perform comprehensive scans of the IPv4 address space, when you are running ZMap, please keep in mind that you are potentially scanning the ENTIRE IPv4 address space at over 1.4 million packets per second. So, before performing even small scans, you should contact the local network administrators and also follow the best practices.

Best Practices:

  • Coordinate closely with local network administrators to reduce risks and handle inquiries
  • Verify that scans will not overwhelm the local network or upstream provider
  • Signal the benign nature of the scans in web pages and DNS entries of the source addresses
  • Clearly explain the purpose and scope of the scans in all communications
  • Provide a simple means of opting out and honor requests promptly
  • Conduct scans no larger or more frequent than is necessary for research objectives
  • Spread scan traffic over time or source addresses when feasible
Also, don’t exploit vulnerabilities or access protected resources.


The latest stable release of ZMap is version 2.1.1 and supports Linux, macOS, and BSD. It can be installed through the built-in package managers on the following operating systems:

Debian and Ubuntu sudo apt install zmap
Fedora, CentOS, and RHEL sudo yum install zmap
Gentoo sudo emerge zmap
macOS (using Homebrew) brew install zmap
Arch Linux sudo pacman -S zmap

ZMap Usage

By default, ZMap will perform a TCP SYN scan on the specified port at the maximum rate possible. A more conservative configuration that will scan 10,000 random addresses on port 80 at a maximum 10 Mbps can be run as follows:

$ zmap --bandwidth=10M --target-port=80 --max-targets=10000 --output-file=results.csv

Or more concisely:

$ zmap -B 10M -p 80 -n 10000 -o results.csv

ZMap can also be used to scan specific subnets or CIDR blocks. For example, to scan only and on TCP/80, run:

$ zmap -p 80

If the scan started successfully, ZMap will output real-time status updates:

0% (1h51m left); send: 28777 562 Kp/s (560 Kp/s avg); recv: 1192 248 p/s (231 p/s avg); hits: 0.04%
0% (1h51m left); send: 34320 554 Kp/s (559 Kp/s avg); recv: 1442 249 p/s (234 p/s avg); hits: 0.04%
0% (1h50m left); send: 39676 535 Kp/s (555 Kp/s avg); recv: 1663 220 p/s (232 p/s avg); hits: 0.04%
0% (1h50m left); send: 45372 570 Kp/s (557 Kp/s avg); recv: 1890 226 p/s (232 p/s avg); hits: 0.04%

These updates provide information about the current state of the scan and are of the following form: %-complete (est time remaining); packets-sent curr-send-rate (avg-send-rate); recv: packets-recv recv-rate (avg-recv-rate); hits: hit-rate.

If you do not know the scan rate that your network can support, you may want to experiment with different scan rates or bandwidth limits to find the fastest rate that your network can support before you see decreased results.

By default, ZMap will output the list of distinct IP addresses that responded successfully (e.g. with a SYN ACK packet) similar to the following. There are several additional formats (e.g. JSON and Redis) for outputting results. Additional output fields can be specified and the results can be filtered using an output filter. [more information]

We strongly encourage you to use a blacklist file, to exclude both reserved/unallocated IP space (e.g. multicast, RFC 1918), as well as networks that request to be excluded from your scans. By default, ZMap will utilize a simple blacklist file containing reserved and unallocated addresses located at /etc/zmap/blacklist.conf. [more information]

If you find yourself specifying certain settings, such as your maximum bandwidth or blacklist file every time you run ZMap, you can specify these in /etc/zmap/zmap.conf or use a custom configuration file.

If you are attempting to troubleshoot scan related issues, there are several options to help debug. First, it is possible can perform a dry run scan in order to see the packets that would be sent over the network by adding the --dryrun flag. As well, it is possible to change the logging verbosity by setting the --verbosity=n flag.


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