Webshell Detection by Keyword

Detects webshells that use GET requests by keyword searches in URL strings

Rule Content

- title: Webshell Detection by Keyword
  id: 7ff9db12-1b94-4a79-ba68-a2402c5d6729
  description: Detects webshells that use GET requests by keyword searches in URL
    strings
  author: Florian Roth
  logsource:
    category: webserver
    product: null
    service: null
  detection:
    keywords:
    - =whoami
    - =net%20user
    - =cmd%20/c%20
    condition: keywords
  fields:
  - client_ip
  - vhost
  - url
  - response
  falsepositives:
  - Web sites like wikis with articles on os commands and pages that include the os
    commands in the URLs
  - User searches in search boxes of the respective website
  level: high

Querying Elasticsearch

Import Libraries



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from elasticsearch import Elasticsearch
from elasticsearch_dsl import Search
import pandas as pd

Initialize Elasticsearch client



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es = Elasticsearch(['http://helk-elasticsearch:9200'])
searchContext = Search(using=es, index='logs-*', doc_type='doc')

Run Elasticsearch Query



In [ ]:

    
s = searchContext.query('query_string', query='\*.keyword:(*\=whoami* OR *\=net%20user* OR *\=cmd%20\/c%20*)')
response = s.execute()
if response.success():
    df = pd.DataFrame((d.to_dict() for d in s.scan()))

Show Results



In [ ]:

    
df.head()