zmap(1) - The Fast Internet Scanner

1. zmap(1)
2. zmap
3. zmap(1)

## NAME

`zmap` - The Fast Internet Scanner

## SYNOPSIS

zmap [ -p <port(s)> ] [ -o <outfile> ] [ OPTIONS... ] [ ip/hostname/range ]

## DESCRIPTION

ZMap is a network tool for scanning the entire IPv4 address space (or large samples). ZMap is capable of scanning the entire Internet in around 45 minutes on a gigabit network connection, reaching ~98% theoretical line speed.

## OPTIONS

### BASIC OPTIONS

`ip`/`hostname`/`range`

  IP addresses or DNS hostnames to scan. Accepts IP ranges in CIDR block notation. Defaults to 0.0.0/8

`-p`, `--target-ports=port(s)`

  List of TCP/UDP ports and/or port ranges to scan (e.g., 80,443,100-105). Use '*' to scan all ports, including port 0.

`-o`, `--output-file=name`

  When using an output module that uses a file, write results to this file. Use - for stdout.

`-b`, `--blocklist-file=path`

  File of subnets to exclude, in CIDR notation, one-per line. It is recommended you use this to exclude RFC 1918 addresses, multicast, IANA reserved space, and other IANA special-purpose addresses. An example blocklist file blocklist.conf for this purpose.

`-w`, `--allowlist-file=path`

  File of subnets to scan, in CIDR notation, one-per line. Specifying a allowlist file is equivalent to specifying to ranges directly on the command line interface, but allows specifying a large number of subnets. Note: if you are specifying a large number of individual IP addresses (more than 10 million), you should instead use `--list-of-ips-file`.

`-I`, `--list-of-ips-file=path`

  File of individual IP addresses to scan, one-per line. This feature allows you to scan a large number of unrelated addresses. If you have a small number of IPs, it is faster to specify these on the command line or by using `--allowlist-file`. This should only be used when scanning more than 10 million addresses. When used in with --allowlist-path, only hosts in the intersection of both sets will be scanned. Hosts specified here, but included in the blocklist will be excluded.

### SCAN OPTIONS

`-r`, `--rate=pps`

  Set the send rate in packets/sec. Note: when combined with --probes, this is total packets per second, not IPs per second. Setting the rate to 0 will scan at full line rate. Default: 10000 pps.

`-B`, `--bandwidth=bps`

  Set the send rate in bits/second (supports suffixes G, M, and K (e.g. -B 10M for 10 mbps). This overrides the --rate flag.

`-n`, `--max-targets=n`

  Cap the number of targets to probe. This can either be a number (e.g. -n 1000) or a percentage (e.g. -n 0.1%) of the scannable address space (after excluding blocklist). A target is an IP/port pair, if scanning multiple ports, and an IP otherwise.

`-N`, `--max-results=n`

  Exit after receiving this many results

`-t`, `--max-runtime=secs`

  Cap the length of time for sending packets

`-c`, `--cooldown-time=secs`

  How long to continue receiving after sending has completed (default=8)

`-e`, `--seed=n`

  Seed used to select address permutation. Use this if you want to scan addresses in the same order for multiple ZMap runs.

`-P`, `--probes=n`

  Number of probes to send to each IP/Port pair (default=1). Since ZMap composes Ethernet frames directly, probes can be lost en-route to destination. Increasing the --probes increases the chance that an online host will receive a probe in an unreliable network. This is contrasted with `--retries` which just gives the number of attempts to send a single probe on the source NIC.

`--retries=n`

  Number of times to try resending a packet if the sendto call fails (default=10)

`--batch=n`

  Number of packets to batch before calling the appropriate syscall to send. Used to take advantage of Linux's `sendmmsg` syscall to send the entire batch at once. Only available on Linux, other OS's will send each packet individually. (default=64)

### SCAN SHARDING

`--shards=N`

  Split the scan up into N shards/partitions among different instances of zmap (default=1). When sharding, --seed is required.

`--shard=n`

  Set which shard to scan (default=0). Shards are 0-indexed in the range [0, N), where N is the total number of shards. When sharding --seed is required.

### NETWORK OPTIONS

`-s`, `--source-port=port|range`

  Source port(s) to send packets from

`-S`, `--source-ip=ip|range`

  Source address(es) to send packets from. Either single IP or range (e.g. 10.0.0.1-10.0.0.9)

`-G`, `--gateway-mac=addr`

  Gateway MAC address to send packets to (in case auto-detection fails)

`--source-mac=addr`

  Source MAC address to send packets from (in case auto-detection fails)

`-i`, `--interface=name`

  Network interface to use

`-X`, `--iplayer`

  Send IP layer packets instead of ethernet packets (for non-Ethernet interface)

`--netmap-wait-ping=ip`

  (Netmap only) Wait for ip to respond to ICMP Echo request before commencing scan. Useful if connected to a switch with STP enabled, where the PHY reset that is needed for entering and leaving Netmap mode will cause the switch to mute the port until the spanning tree protocol has determined that the link should be set into forward state.

### PROBE OPTIONS

ZMap allows users to specify and write their own probe modules. Probe modules are responsible for generating probe packets to send, and processing responses from hosts.

`--list-probe-modules`

  List available probe modules (e.g. tcp_synscan)

`-M`, `--probe-module=name`

  Select probe module (default=tcp_synscan)

`--probe-args=args`

  Arguments to pass to probe module

`--probe-ttl=hops`

  Set TTL value for probe IP packets

`--list-output-fields`

  List the fields the selected probe module can send to the output module

### OUTPUT OPTIONS

ZMap allows users to specify and write their own output modules for use with ZMap. Output modules are responsible for processing the fieldsets returned by the probe module, and outputting them to the user. Users can specify output fields, and write filters over the output fields.

`--list-output-modules`

  List available output modules (e.g. csv)

`-O`, `--output-module=name`

  Select output module (default=csv)

`--output-args=args`

  Arguments to pass to output module

`-f`, `--output-fields=fields`

  Comma-separated list of fields to output

`--output-filter`

  Specify an output filter over the fields defined by the probe module. See the output filter section for more details.

`--no-header-row`

  Excludes any header rows (e.g., CSV header fields) from ZMap output. This is useful if you're piping results into another application that expects only data.

### RESPONSE DEDUPLICATION

Hosts will oftentimes send multiple responses to a probe (either because the scanner doesn't send back a RST packet or because the host has a misimplemented TCP stack. To address this, ZMap will attempt to deduplicate responsive (ip,port) targets.

`--dedup-method`

  Specifies the method ZMap will use to deduplicate responses. Options are: full, window, and none. Full deduplication uses a 32-bit bitmap and guarantees that no duplicates will be emitted. However, full-deduplication requires around 500MB of memory for a single port. We do not support full deduplication for multiple ports. Window uses a sliding window of the last (user-defined) number of responses as set by --dedup-window-size. None will prevent any deduplication.

`--dedup-window-size=targets`

  Specifies the size of the sliding window as the last n target responses to be used for deduplication. Only applicable if using window deduplication.

### LOGGING AND METADATA OPTIONS

`-q`, `--quiet`

  Do not print status updates once per second

`-v`, `--verbosity=n`

  Level of log detail (0-5, default=3)

`-l`, `--log-file=filename`

  Output file for log messages. By default, stderr.

`-m`, `--metadata-file=filename`

  Output file for scan metadata (JSON)

`-L`, `--log-directory`

  Write log entries to a timestamped file in this directory

`-u`, `--status-updates-file`

  Write scan progress updates to CSV file"

`--disable-syslog`

  Disables logging messages to syslog

`--notes`

  Inject user-specified notes into scan metadata

`--user-metadata`

  Inject user-specified JSON metadata into scan metadata

### ADDITIONAL OPTIONS

`-T`, `--sender-threads=n`

  Threads used to send packets. ZMap will attempt to detect the optimal number of send threads based on the number of processor cores. Defaults to min(4, number of processor cores on host - 1).

`-C`, `--config=filename`

  Read a configuration file, which can specify any other options.

`-d`, `--dryrun`

  Print out each packet to stdout instead of sending it (useful for debugging)

`--max-sendto-failures`

  Maximum NIC sendto failures before scan is aborted

`--min-hitrate`

  Minimum hitrate that scan can hit before scan is aborted

`--cores`

  Comma-separated list of cores to pin to

`--ignore-blocklist-errors`

  Ignore invalid, malformed, or unresolvable entries in allowlist/blocklist file. Replaces the pre-v3.x `--ignore-invalid-hosts` option.

`-h`, `--help`

  Print help and exit

`-V`, `--version`

  Print version and exit

### OUTPUT FILTERS

Results generated by a probe module can be filtered before being passed to the output module. Filters are defined over the output fields of a probe module. Filters are written in a simple filtering language, similar to SQL, and are passed to ZMap using the `--output-filter` option. Output filters are commonly used to filter out duplicate results, or to only pass only successful responses to the output module.

Filter expressions are of the form `<fieldname> <operation> <value>`. The type of `<value>` must be either a string or unsigned integer literal, and match the type of `<fieldname>`. The valid operations for integer comparisons are = !=, , , =, =. The operations for string comparisons are =, !=. The `--list-output-fields` flag will print what fields and types are available for the selected probe module, and then exit.

Compound filter expressions may be constructed by combining filter expressions using parenthesis to specify order of operations, the && (logical AND) and || (logical OR) operators.

For example, a filter for only successful, non-duplicate responses would be written as: `--output-filter="success = 1 && repeat = 0"`

### UDP PROBE MODULE OPTIONS

These arguments are all passed using the `--probe-args=args` option. Only one argument may be passed at a time.

`file:/path/to/file`

  Path to payload file to send to each host over UDP.

`template:/path/to/template`

  Path to template file. For each destination host, the template file is populated, set as the UDP payload, and sent.

`text:<text>`

  ASCII text to send to each destination host

`hex:<hex>`

  Hex-encoded binary to send to each destination host

`template-fields`

  Print information about the allowed template fields and exit.

### MID-SCAN CHANGES

You can change the rate at which ZMap is scanning mid-scan by sending SIGUSR1 (increase) and SIGUSR2 (decrease) signals to ZMap. These will result in the scan rate increasing or decreasing by 5%.

1. ZMap
2. April 2024
3. zmap(1)