CrowdSec•3w ago

Ban immediately after scenario is triggered

I adapted one of the scenarios to immediately ban an IP when it requests files like .env or wp. It bans the IP after some time when the url was called but always with a delay. How can I ban immediately? I don't want the requests to reach my server. Is that even possible? because crowdsec would have to read the log and by the time the log is written, it is probably to late. Additional info: When I call domain.tld/.env the alert and the decision are created right away but I can still browse around on the website and open other pages for half a minute until I get banned and when unbanning it always takes half a minute to be unbanned, if that is relevant.

name: http-sensitive-files-local
description: "Detects and blocks attempts to access various common web application scan targets like /.env, WordPress paths, backups, and development leftovers."
type: trigger
labels:
  confidence: 3
  spoofable: 0
  classification:
    - attack.T1595
  behavior: "http:scan"
  label: "HTTP Admin Interface Probing"
  service: http
  remediation: true
filter: |
  evt.Meta.service == 'http' and
  evt.Meta.log_type in ['http_access-log', 'http_error-log'] and
  (
    let uri = Lower(evt.Meta.http_path);
    uri contains "/.env" or
    uri contains "/wp" or
    uri startsWith "/wordpress" or
    uri startsWith "/bak" or
    uri startsWith "/backup" or
    uri startsWith "/old" or
    uri startsWith "/new" or
    uri startsWith "/main" or
    uri startsWith "/.sql" or
    uri startsWith "/.zip" or
    uri startsWith "/.rar" or
    uri startsWith "/.tar.gz" or
    uri startsWith "/.bak" or
    uri startsWith "/.git/config"
  )

groupby: "evt.Meta.source_ip"

name: http-sensitive-files-local
description: "Detects and blocks attempts to access various common web application scan targets like /.env, WordPress paths, backups, and development leftovers."
type: trigger
labels:
  confidence: 3
  spoofable: 0
  classification:
    - attack.T1595
  behavior: "http:scan"
  label: "HTTP Admin Interface Probing"
  service: http
  remediation: true
filter: |
  evt.Meta.service == 'http' and
  evt.Meta.log_type in ['http_access-log', 'http_error-log'] and
  (
    let uri = Lower(evt.Meta.http_path);
    uri contains "/.env" or
    uri contains "/wp" or
    uri startsWith "/wordpress" or
    uri startsWith "/bak" or
    uri startsWith "/backup" or
    uri startsWith "/old" or
    uri startsWith "/new" or
    uri startsWith "/main" or
    uri startsWith "/.sql" or
    uri startsWith "/.zip" or
    uri startsWith "/.rar" or
    uri startsWith "/.tar.gz" or
    uri startsWith "/.bak" or
    uri startsWith "/.git/config"
  )

groupby: "evt.Meta.source_ip"

6 Replies

CrowdSec•3w ago

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_KaszpiR_•3w ago

A lot depends on your remediation component - how frequently it gets updates from the lapi and how it applies the remediation ( thus if it for example blocks new connections but keeps the open ones)

iiamloz•3w ago

How can I ban immediately? I don't want the requests to reach my server.

Then you have to use something to block the request midway, so a WAF https://docs.crowdsec.net/docs/next/appsec/intro

AppSec Component - CrowdSec WAF | CrowdSec

Introduction

iiamloz•3w ago

also you most likely want to do a endsWith on these

    uri startsWith "/.sql" or
    uri startsWith "/.zip" or
    uri startsWith "/.rar" or
    uri startsWith "/.tar.gz" or
    uri startsWith "/.bak" or
    uri startsWith "/.git/config"

    uri startsWith "/.sql" or
    uri startsWith "/.zip" or
    uri startsWith "/.rar" or
    uri startsWith "/.tar.gz" or
    uri startsWith "/.bak" or
    uri startsWith "/.git/config"

as you shouldnt care I look for /foo/bar/test.sql I prefer to write my rules in raw seclang but let me know and I can convert it to our DSL but here an example blocking programming UA's

#/etc/crowdsec/appsec-rules/myrules.yaml
name: my/rules
description: "Custom inband rules"
seclang_rules:
  - |
    SecRule REQUEST_HEADERS:User-Agent "^(?:go-http|python|curl|wget|nmap|sqlmap|guzzle|wpscan|scrapy|colly)" "id:10004, phase:1, deny, t:lowercase, msg: 'Programming UA Header: %{MATCHED_VAR}'"

#/etc/crowdsec/appsec-rules/myrules.yaml
name: my/rules
description: "Custom inband rules"
seclang_rules:
  - |
    SecRule REQUEST_HEADERS:User-Agent "^(?:go-http|python|curl|wget|nmap|sqlmap|guzzle|wpscan|scrapy|colly)" "id:10004, phase:1, deny, t:lowercase, msg: 'Programming UA Header: %{MATCHED_VAR}'"

iiamloz•3w ago

then it blocks these requests before they get to my backend

UnaviOP•3w ago

Thank you! I enabled WAF and now the requests get blocked. When going back to a normal url I still am able to access it for a few seconds before the ip gets banned. This is my profiles.yaml with the remediation settings.

name: default_ip_remediation
debug: true
filters:
 - Alert.Remediation == true && Alert.GetScope() == "Ip"
decisions:
 - type: ban
   duration: 30m
duration_expr: Sprintf('%dh', (GetDecisionsCount(Alert.GetValue()) + 1) * 4)
notifications:
 - http_victoriametrics
# notifications:
#   - slack_default  # Set the webhook in /etc/crowdsec/notifications/slack.yaml before enabling this.
#   - splunk_default # Set the splunk url and token in /etc/crowdsec/notifications/splunk.yaml before enabling this.
#   - http_default   # Set the required http parameters in /etc/crowdsec/notifications/http.yaml before enabling this.
#   - email_default  # Set the required email parameters in /etc/crowdsec/notifications/email.yaml before enabling this.
on_success: break
---
name: default_range_remediation
#debug: true
filters:
 - Alert.Remediation == true && Alert.GetScope() == "Range"
decisions:
 - type: ban
   duration: 30m
#duration_expr: Sprintf('%dh', (GetDecisionsCount(Alert.GetValue()) + 1) * 4)
# notifications:
#   - slack_default  # Set the webhook in /etc/crowdsec/notifications/slack.yaml before enabling this.
#   - splunk_default # Set the splunk url and token in /etc/crowdsec/notifications/splunk.yaml before enabling this.
#   - http_default   # Set the required http parameters in /etc/crowdsec/notifications/http.yaml before enabling this.
#   - email_default  # Set the required email parameters in /etc/crowdsec/notifications/email.yaml before enabling this.
on_success: break

name: default_ip_remediation
debug: true
filters:
 - Alert.Remediation == true && Alert.GetScope() == "Ip"
decisions:
 - type: ban
   duration: 30m
duration_expr: Sprintf('%dh', (GetDecisionsCount(Alert.GetValue()) + 1) * 4)
notifications:
 - http_victoriametrics
# notifications:
#   - slack_default  # Set the webhook in /etc/crowdsec/notifications/slack.yaml before enabling this.
#   - splunk_default # Set the splunk url and token in /etc/crowdsec/notifications/splunk.yaml before enabling this.
#   - http_default   # Set the required http parameters in /etc/crowdsec/notifications/http.yaml before enabling this.
#   - email_default  # Set the required email parameters in /etc/crowdsec/notifications/email.yaml before enabling this.
on_success: break
---
name: default_range_remediation
#debug: true
filters:
 - Alert.Remediation == true && Alert.GetScope() == "Range"
decisions:
 - type: ban
   duration: 30m
#duration_expr: Sprintf('%dh', (GetDecisionsCount(Alert.GetValue()) + 1) * 4)
# notifications:
#   - slack_default  # Set the webhook in /etc/crowdsec/notifications/slack.yaml before enabling this.
#   - splunk_default # Set the splunk url and token in /etc/crowdsec/notifications/splunk.yaml before enabling this.
#   - http_default   # Set the required http parameters in /etc/crowdsec/notifications/http.yaml before enabling this.
#   - email_default  # Set the required email parameters in /etc/crowdsec/notifications/email.yaml before enabling this.
on_success: break

That looks neat. This would block common crawler tools? Do I understand correctly that the appsec rules also ban like scenarios? but they only run for waf and not for the logs? And scenarios are treated as In-band rules for the waf? I think ideally I would want a seclang rule or new dsl that blocks all access to requests ending with certain keywords like .env and it would read the keywords from a new line separated list out of a txt file that is in the same folder as the rule. Is that possible and could you write me something like that? or point me to resources that explain that? I read over https://docs.crowdsec.net/docs/appsec/rules_syntax/ I guess you prefere seclang because you are used to it and you already have a lot of rules written in it?

Gaming

Programming

Ban immediately after scenario is triggered

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