はじめに
Linuxが普及してきたので、ウイルス対策なしのノーガード戦法は怖い。
無料のウイルス対策ソフトのClamAVを入れておこう。
環境
動作環境は以下の通り。
Ubuntu
$ cat /etc/os-release
NAME="Ubuntu"
VERSION="20.04.2 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.2 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal
ClamAV
$ clamd --version
ClamAV 0.103.2/26226/Fri Jul 9 20:16:15 2021
$ sudo apt list --installed | grep clam
clamav-base/focal-updates,focal-updates,focal-security,focal-security,now 0.103.2+dfsg-0ubuntu0.20.04.2 all [インストール済み、自動]
clamav-daemon/focal-updates,focal-security,now 0.103.2+dfsg-0ubuntu0.20.04.2 amd64 [インストール済み]
clamav-freshclam/focal-updates,focal-security,now 0.103.2+dfsg-0ubuntu0.20.04.2 amd64 [インストール済み、自動]
clamav/focal-updates,focal-security,now 0.103.2+dfsg-0ubuntu0.20.04.2 amd64 [インストール済み]
clamdscan/focal-updates,focal-security,now 0.103.2+dfsg-0ubuntu0.20.04.2 amd64 [インストール済み、自動]
clamtk/focal,focal,now 6.02-1 all [インストール済み]
libclamav9/focal-updates,focal-security,now 0.103.2+dfsg-0ubuntu0.20.04.2 amd64 [インストール済み、自動]
手順
インストール
以下のコマンドでインストール。
sudo apt install clamav clamav-daemon
サービス起動
clamavデーモン
まず、clamavデーモンを起動する。
clamavデーモンは、clamdscanコマンドからの指示を受信してマルチスレッドでウイルススキャンをするサービス。
$ sudo systemctl start clamav-daemon.service
$ sudo systemctl status clamav-daemon.service
● clamav-daemon.service - Clam AntiVirus userspace daemon
Loaded: loaded (/lib/systemd/system/clamav-daemon.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/clamav-daemon.service.d
└─extend.conf
Active: active (running) since Fri 2021-07-09 06:35:27 JST; 1 day 9h ago
Docs: man:clamd(8)
man:clamd.conf(5)
https://www.clamav.net/documents/
Main PID: 1113 (clamd)
Tasks: 2 (limit: 38399)
Memory: 1.1G
CGroup: /system.slice/clamav-daemon.service
└─1113 /usr/sbin/clamd --foreground=true
clamavアップデータ
次に、clamavアップデータを起動する。
これが起動していると、自動的にウイルス定義ファイルを更新してくれる。
$ sudo systemctl start clamav-freshclam.service
$ sudo systemctl status clamav-freshclam.service
● clamav-freshclam.service - ClamAV virus database updater
Loaded: loaded (/lib/systemd/system/clamav-freshclam.service; enabled; vendor preset: enabled)
Active: active (running) since Fri 2021-07-09 06:35:33 JST; 1 day 9h ago
Docs: man:freshclam(1)
man:freshclam.conf(5)
https://www.clamav.net/documents
Main PID: 1578 (freshclam)
Tasks: 1 (limit: 38399)
Memory: 297.4M
CGroup: /system.slice/clamav-freshclam.service
└─1578 /usr/bin/freshclam -d --foreground=true
手動検索
手動で検索してみる。
sudo clamdscan /path/to/scan/target
定期自動検索
clamav自体には、定期的に自動検索する機能はない。
cronでclamavを定期的に実行して、定期スキャンを実現する。
ここで、clamavには性質の異なる2つのコマンドが用意されているため、インストールする環境にあったコマンドを利用することをおすすめする。
| コマンド | メリット | デメリット |
|---|---|---|
| clamscan | オプションが豊富 daemon不要 |
遅い |
| clamdscan | 早い マルチスレッド実行可 |
オプションが少ない daemon必要 |
実行速度
clamdscanは、マルチスレッド実行可。
ClamdTOP version 0.103.2 Sat Jul 10 17:27:17 2021
NO CONNTIME LIV IDL QUEUE MAXQ MEM ENGINE DBVER DBTIME HOST
1 00:00:07 12 0 50 50 1.27G 0.103.2 26226 2021-07-09T20 local
Details for Clamd version: ClamAV 0.103.2/26226/Fri Jul 9 20:16:15 2021
Primary threads: live 12 idle 0 max 12 ┌───────────────────────────────────────┐
[||||||||||||||||||||||||||||||||||||] │Mem: heap 184M mmap 0M unused 0M│
Queue: 50 items 50 max │Libc: used 19M free 165M total 184M│
[||||||||||||||||||||||||||||||||||||] │Pool: count 1 used 1116M total 1116M│
│[||||||||||||||||||||||||||||||||||||] │
└───────────────────────────────────────┘
COMMAND QUEUEDSINCE FILE
FILDES 49.713s fd[31]
FILDES 5.343s fd[22]
FILDES 5.308s fd[41]
FILDES 3.684s fd[66]
FILDES 3.108s fd[19]
FILDES 1.848s fd[36]
FILDES 1.291s fd[34]
FILDES 0.016s fd[38]
FILDES 0.011s fd[54]
FILDES 0.009s fd[52]
FILDES 0.000s fd[57]
STATS 0.000s
オプション
clamscanのオプションは数十個。
$ clamscan --help
Clam AntiVirus: Scanner 0.103.2
By The ClamAV Team: https://www.clamav.net/about.html#credits
(C) 2021 Cisco Systems, Inc.
clamscan [options] [file/directory/-]
--help -h Show this help
--version -V Print version number
--verbose -v Be verbose
--archive-verbose -a Show filenames inside scanned archives
--debug Enable libclamav's debug messages
--quiet Only output error messages
--stdout Write to stdout instead of stderr. Does not affect 'debug' messages.
--no-summary Disable summary at end of scanning
--infected -i Only print infected files
--suppress-ok-results -o Skip printing OK files
--bell Sound bell on virus detection
--tempdir=DIRECTORY Create temporary files in DIRECTORY
--leave-temps[=yes/no(*)] Do not remove temporary files
--gen-json[=yes/no(*)] Generate JSON description of scanned file(s). JSON will be printed and also-
dropped to the temp directory if --leave-temps is enabled.
--database=FILE/DIR -d FILE/DIR Load virus database from FILE or load all supported db files from DIR
--official-db-only[=yes/no(*)] Only load official signatures
--log=FILE -l FILE Save scan report to FILE
--recursive[=yes/no(*)] -r Scan subdirectories recursively
--allmatch[=yes/no(*)] -z Continue scanning within file after finding a match
--cross-fs[=yes(*)/no] Scan files and directories on other filesystems
--follow-dir-symlinks[=0/1(*)/2] Follow directory symlinks (0 = never, 1 = direct, 2 = always)
--follow-file-symlinks[=0/1(*)/2] Follow file symlinks (0 = never, 1 = direct, 2 = always)
--file-list=FILE -f FILE Scan files from FILE
--remove[=yes/no(*)] Remove infected files. Be careful!
--move=DIRECTORY Move infected files into DIRECTORY
--copy=DIRECTORY Copy infected files into DIRECTORY
--exclude=REGEX Don't scan file names matching REGEX
--exclude-dir=REGEX Don't scan directories matching REGEX
--include=REGEX Only scan file names matching REGEX
--include-dir=REGEX Only scan directories matching REGEX
--bytecode[=yes(*)/no] Load bytecode from the database
--bytecode-unsigned[=yes/no(*)] Load unsigned bytecode
**Caution**: You should NEVER run bytecode signatures from untrusted sources.
Doing so may result in arbitrary code execution.
--bytecode-timeout=N Set bytecode timeout (in milliseconds)
--statistics[=none(*)/bytecode/pcre] Collect and print execution statistics
--detect-pua[=yes/no(*)] Detect Possibly Unwanted Applications
--exclude-pua=CAT Skip PUA sigs of category CAT
--include-pua=CAT Load PUA sigs of category CAT
--detect-structured[=yes/no(*)] Detect structured data (SSN, Credit Card)
--structured-ssn-format=X SSN format (0=normal,1=stripped,2=both)
--structured-ssn-count=N Min SSN count to generate a detect
--structured-cc-count=N Min CC count to generate a detect
--structured-cc-mode=X CC mode (0=credit debit and private label, 1=credit cards only
--scan-mail[=yes(*)/no] Scan mail files
--phishing-sigs[=yes(*)/no] Enable email signature-based phishing detection
--phishing-scan-urls[=yes(*)/no] Enable URL signature-based phishing detection
--heuristic-alerts[=yes(*)/no] Heuristic alerts
--heuristic-scan-precedence[=yes/no(*)] Stop scanning as soon as a heuristic match is found
--normalize[=yes(*)/no] Normalize html, script, and text files. Use normalize=no for yara compatibility
--scan-pe[=yes(*)/no] Scan PE files
--scan-elf[=yes(*)/no] Scan ELF files
--scan-ole2[=yes(*)/no] Scan OLE2 containers
--scan-pdf[=yes(*)/no] Scan PDF files
--scan-swf[=yes(*)/no] Scan SWF files
--scan-html[=yes(*)/no] Scan HTML files
--scan-xmldocs[=yes(*)/no] Scan xml-based document files
--scan-hwp3[=yes(*)/no] Scan HWP3 files
--scan-archive[=yes(*)/no] Scan archive files (supported by libclamav)
--alert-broken[=yes/no(*)] Alert on broken executable files (PE & ELF)
--alert-broken-media[=yes/no(*)] Alert on broken graphics files (JPEG, TIFF, PNG, GIF)
--alert-encrypted[=yes/no(*)] Alert on encrypted archives and documents
--alert-encrypted-archive[=yes/no(*)] Alert on encrypted archives
--alert-encrypted-doc[=yes/no(*)] Alert on encrypted documents
--alert-macros[=yes/no(*)] Alert on OLE2 files containing VBA macros
--alert-exceeds-max[=yes/no(*)] Alert on files that exceed max file size, max scan size, or max recursion limit
--alert-phishing-ssl[=yes/no(*)] Alert on emails containing SSL mismatches in URLs
--alert-phishing-cloak[=yes/no(*)] Alert on emails containing cloaked URLs
--alert-partition-intersection[=yes/no(*)] Alert on raw DMG image files containing partition intersections
--nocerts Disable authenticode certificate chain verification in PE files
--dumpcerts Dump authenticode certificate chain in PE files
--max-scantime=#n Scan time longer than this will be skipped and assumed clean (milliseconds)
--max-filesize=#n Files larger than this will be skipped and assumed clean
--max-scansize=#n The maximum amount of data to scan for each container file (**)
--max-files=#n The maximum number of files to scan for each container file (**)
--max-recursion=#n Maximum archive recursion level for container file (**)
--max-dir-recursion=#n Maximum directory recursion level
--max-embeddedpe=#n Maximum size file to check for embedded PE
--max-htmlnormalize=#n Maximum size of HTML file to normalize
--max-htmlnotags=#n Maximum size of normalized HTML file to scan
--max-scriptnormalize=#n Maximum size of script file to normalize
--max-ziptypercg=#n Maximum size zip to type reanalyze
--max-partitions=#n Maximum number of partitions in disk image to be scanned
--max-iconspe=#n Maximum number of icons in PE file to be scanned
--max-rechwp3=#n Maximum recursive calls to HWP3 parsing function
--pcre-match-limit=#n Maximum calls to the PCRE match function.
--pcre-recmatch-limit=#n Maximum recursive calls to the PCRE match function.
--pcre-max-filesize=#n Maximum size file to perform PCRE subsig matching.
--disable-cache Disable caching and cache checks for hash sums of scanned files.
Pass in - as the filename for stdin.
(*) Default scan settings
(**) Certain files (e.g. documents, archives, etc.) may in turn contain other
files inside. The above options ensure safe processing of this kind of data.
clamdscanのオプションは、せいぜい10個程度
$ clamdscan --help
Clam AntiVirus: Daemon Client 0.103.2
By The ClamAV Team: https://www.clamav.net/about.html#credits
(C) 2021 Cisco Systems, Inc.
clamdscan [options] [file/directory/-]
--help -h Show this help
--version -V Print version number and exit
--verbose -v Be verbose
--quiet Be quiet, only output error messages
--stdout Write to stdout instead of stderr. Does not affect 'debug' messages.
(this help is always written to stdout)
--log=FILE -l FILE Save scan report in FILE
--file-list=FILE -f FILE Scan files from FILE
--ping -p A[:I] Ping clamd up to [A] times at optional interval [I] until it responds.
--wait -w Wait up to 30 seconds for clamd to start. Optionally use alongside --ping to set attempts [A] and interval [I] to check clamd.
--remove Remove infected files. Be careful!
--move=DIRECTORY Move infected files into DIRECTORY
--copy=DIRECTORY Copy infected files into DIRECTORY
--config-file=FILE Read configuration from FILE.
--allmatch -z Continue scanning within file after finding a match.
--multiscan -m Force MULTISCAN mode
--infected -i Only print infected files
--no-summary Disable summary at end of scanning
--reload Request clamd to reload virus database
--fdpass Pass filedescriptor to clamd (useful if clamd is running as a different user)
--stream Force streaming files to clamd (for debugging and unit testing)
スクリプト作成
次にcronから呼び出すスクリプトを作成する。
clamscanを使用する場合
clamscanを使用した例は以下。
scan.sh
#!/bin/bash
/usr/bin/clamscan \
--exclude-dir=/path/to/exlude/directories \
--exclude-dir=/path/to/exlude/directories \
-i \
-r $HOME \
--log="$HOME/.clamtk/history/$(date +\%Y\%m\%d-\%H\%M\%S).log" \
2>/dev/null
clamdscanを使用する場合
clamdscanを使用した例は以下。
mkdir -p $HOME/.clamtk/virus
mkdir -p $HOME/.clamtk/history
find $HOME -type d | xargs clamdscan \
--infected \
--multiscan \
--fdpass \
--move="$HOME/.clamtk/virus" \
--log="$HOME/.clamtk/history/$(date +\%Y\%m\%d-\%H\%M\%S).log"
ポイントは、 --multiscan オプション。
これで、マルチスレッドでスキャンができて早い。
ただし、重い・・・。
crontabの設定
crontab にスクリプトを設定する。
crontab
$ crontab -e
$ crontab -l | grep clamscan
0 20 * * * bash /path/to/scan.sh