{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Suspicious VSFTPD Error Messages\n",
    "Detects suspicious VSFTPD error messages that indicate a fatal or suspicious error that could be caused by exploiting attempts"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Rule Content\n",
    "```\n",
    "- title: Suspicious VSFTPD Error Messages\n",
    "  id: 377f33a1-4b36-4ee1-acee-1dbe4b43cfbe\n",
    "  description: Detects suspicious VSFTPD error messages that indicate a fatal or suspicious\n",
    "    error that could be caused by exploiting attempts\n",
    "  references:\n",
    "  - https://github.com/dagwieers/vsftpd/\n",
    "  author: Florian Roth\n",
    "  date: 2017/07/05\n",
    "  logsource:\n",
    "    product: linux\n",
    "    service: vsftpd\n",
    "    category: null\n",
    "  detection:\n",
    "    keywords:\n",
    "    - 'Connection refused: too many sessions for this address.'\n",
    "    - 'Connection refused: tcp_wrappers denial.'\n",
    "    - Bad HTTP verb.\n",
    "    - port and pasv both active\n",
    "    - pasv and port both active\n",
    "    - Transfer done (but failed to open directory).\n",
    "    - Could not set file modification time.\n",
    "    - 'bug: pid active in ptrace_sandbox_free'\n",
    "    - PTRACE_SETOPTIONS failure\n",
    "    - 'weird status:'\n",
    "    - couldn't handle sandbox event\n",
    "    - syscall * out of bounds\n",
    "    - 'syscall not permitted:'\n",
    "    - 'syscall validate failed:'\n",
    "    - Input line too long.\n",
    "    - poor buffer accounting in str_netfd_alloc\n",
    "    - vsf_sysutil_read_loop\n",
    "    condition: keywords\n",
    "  falsepositives:\n",
    "  - Unknown\n",
    "  level: medium\n",
    "\n",
    "```"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Querying Elasticsearch"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Import Libraries"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "from elasticsearch import Elasticsearch\n",
    "from elasticsearch_dsl import Search\n",
    "import pandas as pd"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Initialize Elasticsearch client"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "es = Elasticsearch(['http://helk-elasticsearch:9200'])\n",
    "searchContext = Search(using=es, index='logs-*', doc_type='doc')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Run Elasticsearch Query"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "s = searchContext.query('query_string', query='\\*.keyword:(*Connection\\ refused\\:\\ too\\ many\\ sessions\\ for\\ this\\ address.* OR *Connection\\ refused\\:\\ tcp_wrappers\\ denial.* OR *Bad\\ HTTP\\ verb.* OR *port\\ and\\ pasv\\ both\\ active* OR *pasv\\ and\\ port\\ both\\ active* OR *Transfer\\ done\\ \\(but\\ failed\\ to\\ open\\ directory\\).* OR *Could\\ not\\ set\\ file\\ modification\\ time.* OR *bug\\:\\ pid\\ active\\ in\\ ptrace_sandbox_free* OR *PTRACE_SETOPTIONS\\ failure* OR *weird\\ status\\:* OR *couldn't\\ handle\\ sandbox\\ event* OR *syscall\\ *\\ out\\ of\\ bounds* OR *syscall\\ not\\ permitted\\:* OR *syscall\\ validate\\ failed\\:* OR *Input\\ line\\ too\\ long.* OR *poor\\ buffer\\ accounting\\ in\\ str_netfd_alloc* OR *vsf_sysutil_read_loop*)')\n",
    "response = s.execute()\n",
    "if response.success():\n",
    "    df = pd.DataFrame((d.to_dict() for d in s.scan()))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Show Results"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "df.head()"
   ]
  }
 ],
 "metadata": {},
 "nbformat": 4,
 "nbformat_minor": 4
}