Awesome Open Source
Awesome Open Source


You are seeing an ergonomic, asynchronous, and fully customisable implementation of Low & Slow load generator designed for real-world pentesting. It can be completely undetectable by proxifying all the connections.

Table of contents


  • Asynchronous. Finshir uses the Tokio runtime for asynchronous I/O to reduce the CPU load significantly and make the program portable between multiple platforms (Windows, GNU/Linux, Mac OS, and other).

  • Generic. Unlike other Low & Slow utilities, Finshir lets you transmit arbitrary data sets over the TCP protocol. It may be partial HTTP headers, empty spaces, and so on.

  • Written in Rust. How you can see, all the logic is written completely in Rust, which means that it leverages bare-metal performance and high-level safety (no SIGSEGV, SIGILL, and other "funny" stuff).


Building from

$ cargo install finshir

Building from sources

$ git clone
$ cd finshir
$ cargo build --release

Pre-compiled binaries

$ wget
$ chmod a+x finshir-x86_64-linux



Name Explanation
-h, --help Prints help information
--use-tls Use a TLS connection instead of the ordinary TCP protocol. It might be used to test HTTPS-based services
-V, --version Prints version information


Name Value Default Explanation
--connect-periodicity Time span 7secs This option will be applied if a socket connection error occurs (the next connection will be performed after this periodicity)
--connect-timeout Time span 10secs If a timeout is reached and a socket hasn't been connected, the program will retry the operation later
--connections Positive integer 1000 A number of connections the program will handle simultaneously. This option also equals to a number of concurrent tasks
--date-time-format String %X A format for displaying local date and time in log messages. Type man strftime to see the format specification
--ip-ttl Unsigned integer 64 Specifies the IP_TTL value for all future sockets. Usually this value equals a number of routers that a packet can go through
--json-report Filename None A file to which a JSON report (also called a "total summary") will be generated before exiting
-f, --portions-file Filename None A file which consists of a custom JSON array of data portions, specified as strings.

When a task finished sending all portions, it reconnects its socket and starts sending them again.
-r, --receiver Socket address None A receiver of generator traffic, specified as an IP address (or a domain name) and a port number, separated by a colon
-d, --test-duration Time span 64years 64hours 64secs A whole test duration, after which all spawned tasks will stop their work
--trust-cert-der Filename None A DER-encoded TLS certificate file to trust while establishing a TLS connection. Can be specified several times
--trust-cert-pem Filename None A PEM-encoded TLS certificate file to trust while establishing a TLS connection. Can be specified several times
--txt-report Filename None A file to which the program will generate a human-readable report (also called a "total summary") before exiting
-v, --verbosity From 0 to 5 3 Enable one of the possible verbosity levels. The zero level doesn't print anything, and the last level prints everything.

Note that specifying the 4 and 5 verbosity levels might decrease performance, do it only for debugging.
-w, --wait Time span 5secs A waiting time span before test execution used to prevent a launch of an erroneous (unwanted) test
--write-periodicity Time span 30secs A time interval between writing data portions. This option can be used to modify test intensity
--xml-report Filename None A file to which an XML report (also called a "total summary") will be generated before exiting
-p, --proxy Proxy format None Adds a new SOCKS5 proxy to a list of proxies to use. It accepts either an address or a string of a format [email protected]@PASSWORD.

Every new TCP connection will be proxified through a random proxy in a list of all proxies you specified.


Minimal command

The following command spawns 1000 tasks, each trying to establish a new TCP connection. When connections are established, it sends empty spaces every 30 seconds, thereby order a server to wait as long as it can:

# Specify one of the Google's IP addresses as a target web server
$ finshir

Test intensity

Low & Slow techniques assume to be VERY SLOW, which means that you typically send a couple of bytes every N seconds. For instance, Finshir uses the 30 seconds interval by default, but it's modifiable as well:

# Test the Google's server sending data portions every one minute
$ finshir --write-periodicity=1min

Using a list of proxies

You can use the --proxy option to specify as many proxies as you want, Finshir will proxify a new connection through a random one. This option can be specified both as <ADDRESS> or as <[email protected]@PASSWORD>.

# Test the Google's server using the local proxy
$ finshir --proxy=

# Test the Google's server using the same proxy with authentication
$ finshir --proxy=[email protected]@Password123

The default Tor proxy creates a new circuit for each (login, password) pair. That is, if you specify 30 unique (login, password) pairs, then Finshir will torify its traffic through 30 different circuits.

# Test the Google's server using eight Tor circuits created by
# (a default Tor proxy address):
$ finshir \
--proxy=[email protected]@Password1 \
--proxy=[email protected]@Password2 \
--proxy=[email protected]@Password3 \
--proxy=[email protected]@Password4 \
--proxy=[email protected]@Password5 \
--proxy=[email protected]@Password6 \
--proxy=[email protected]@Password7 \
--proxy=[email protected]@Password8

Connections count

The default number of parallel connections is 1000. However, you can modify this limit using the --connections option, but be sure that you system is able to handle such amount of file descriptors:

# Modify the default limit of file descriptors to 17015
$ sudo ulimit -n 17015

# Test the target server using 17000 parallel TCP connections
$ finshir --connections=17000

TLS support

Most of web servers today use the HTTPS protocol instead of HTTP, which is based on TLS. Since v0.2.0, Finshir has functionality to connect through TLS using the --use-tls flag.

# Connect to the Google's server through TLS on 443 port (HTTPS)
$ finshir --use-tls

Logging options

Consider specifying a custom verbosity level from 0 to 5 (inclusively), which is done by the --verbosity option. There is also the --date-time-format option which tells Finshir to use your custom date-time format.

# Use a custom date-time format and the last verbosity level
$ finshir --date-time-format="%F" --verbosity=5

Different verbosity levels print different logging types. As you can see in the table below, the zero verbosity level prints nothing, and the last one prints everything. The levels in the middle print logs selectively:

Errors Warnings Notifications Debugs Traces
Zero (0) āŒ āŒ āŒ āŒ āŒ
First (1) āœ” āŒ āŒ āŒ āŒ
Second (2) āœ” āœ” āŒ āŒ āŒ
Third (3) āœ” āœ” āœ” āŒ āŒ
Fourth (4) āœ” āœ” āœ” āœ” āŒ
Fifth (5) āœ” āœ” āœ” āœ” āœ”

Custom data portions

By default, Finshir generates 100 empty spaces as data portions to send. You can override this behaviour by specifying your custom messages as a file, consisting of a single JSON array. This example is focused on Google:

# Send partial HTTP headers to Google using `--portions-file`
$ finshir -f files/google.json --use-tls

The command above sends a partial HTTPS request (first introduced by Slowloris) through TLS (which is achieved by specifying the --use-tls flag). You can access this partial request inside files/google.json.


  "GET HTTP/1.1\r\n",
  "User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:66.0) Gecko/20100101 Firefox/66.0\r\n",
  "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n",
  "Accept-Language: en-US,en;q=0.5\r\n",
  "Accept-Encoding: gzip, deflate, br\r\n",
  "Connection: keep-alive\r\n",
  "Upgrade-Insecure-Requests: 1\r\n",
  "Cache-Control: max-age=0\r\n",
  "TE: Trailers\r\n",

Generate a report

Report is a set of test-specific variables like a total number of connections established, a receiver, an execution duration and so on. There is three options for this: --xml-report, --json-report, and --txt-report:

# Test the Google's server and generate JSON and XML reports at the end
$ finshir --json-report=report.json --xml-report=report.xml

"At the end" means if allotted time expires or if you cancel the process by Ctrl-C. Also, statistics will being printed to a terminal after every three seconds. You can look at the report examples in the files/example_reports folder:


  "connections": {
    "failed": 0,
    "successful": 50,
    "total": 50
  "receiver": "",
  "time": {
    "test-duration": "10s 478ms 501us 187ns",
    "test-start": "Thu, 05 Sep 2019 08:15:13 -0000",
    "text-end": "Thu, 05 Sep 2019 08:15:24 -0000"
  "total-bytes-sent": 50,
  "total-errors": 0,
  "transmissions": {
    "failed": 0,
    "successful": 50,
    "total": 50


<?xml version="1.0" encoding="UTF-8"?>
    <test-start>Thu, 05 Sep 2019 08:15:13 -0000</test-start>
    <test-end>Thu, 05 Sep 2019 08:15:24 -0000</test-end>
    <test-duration>10s 480ms 351us 533ns</test-duration>


*********************** FINSHIR REPORT ***********************
Total bytes sent:         50
Total errors:             0

Test start:               Thu, 05 Sep 2019 08:15:13 -0000
Test end:                 Thu, 05 Sep 2019 08:15:24 -0000
Test duration:            10s 482ms 821us 872ns

Successful connections:   50
Failed connections:       0
Total connections:        50

Successful transmissions: 50
Failed transmissions:     0
Total transmissions:      50


You are always welcome for any contribution to this project! But before you start, you should read the appropriate document to know about the preferred development process and the basic communication rules.

Legal disclaimer

Finshir was developed as a means of testing stress resistance of web servers, and not for hacking, that is, the author of the project IS NOT RESPONSIBLE for any damage caused by your use of his program.


Temirkhan Myrzamadi <[email protected]> (the author)

Get A Weekly Email With Trending Projects For These Topics
No Spam. Unsubscribe easily at any time.
rust (3,979)Ā 
http (858)Ā 
tcp (221)Ā 
high-performance (179)Ā 
pentest-tool (114)Ā 
rust-crate (25)Ā 
tor-network (20)Ā 
stress-testing (17)Ā 

Find Open Source By Browsing 7,000 Topics Across 59 Categories