sshのログから認証失敗のIPを抽出してブロックするDenyHostsをインストールしてみました
DenyHosts
http://denyhosts.sourceforge.net/
参考サイト
DenyHosts で ssh ブルートフォースアタック対策
http://www.maruko2.com/mw/DenyHosts_%E3%81%A7_ssh_%E3%83%96%E3%83%AB%E3%83%BC%E3%83%88%E3%83%95%E3%82%A9%E3%83%BC%E3%82%B9%E3%82%A2%E3%82%BF%E3%83%83%E3%82%AF%E5%AF%BE%E7%AD%96
- DenyHostsをインストール
- 設定ファイルの編集
- 自動起動の設定
- 常に許可するIPを設定
- DenyHostsの開始
いつものようにyumを使ってインストールします
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[root@host1 ~]# yum info DenyHosts Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * addons: ftp.riken.jp * base: ftp.riken.jp * centosplus: ftp.riken.jp * epel: ftp.riken.jp * extras: ftp.riken.jp * remi: mirrors.mediatemple.net * updates: ftp.riken.jp addons | 1.9 kB 00:00 base | 1.1 kB 00:00 centosplus | 1.9 kB 00:00 dag | 1.9 kB 00:00 epel | 3.6 kB 00:00 extras | 2.1 kB 00:00 remi | 2.5 kB 00:00 updates | 1.9 kB 00:00 Available Packages Name : denyhosts Arch : noarch Version : 2.6 Release : 5.el5 Size : 98 k Repo : epel Summary : A script to help thwart ssh server attacks URL : http://denyhosts.sourceforge.net/ License : GPL Description: DenyHosts is a Python script that analyzes the sshd server log : messages to determine which hosts are attempting to hack into your : system. It also determines what user accounts are being targeted. : It keeps track of the frequency of attempts from each host and, : upon discovering a repeated attack host, updates the : /etc/hosts.deny file to prevent future break-in attempts from that : host. Email reports can be sent to a system admin. [root@host1 ~]# yum install denyhosts Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * addons: ftp.riken.jp * base: ftp.riken.jp * centosplus: ftp.riken.jp * epel: ftp.riken.jp * extras: ftp.riken.jp * remi: mirrors.mediatemple.net * updates: ftp.riken.jp Setting up Install Process Resolving Dependencies --> Running transaction check ---> Package denyhosts.noarch 0:2.6-5.el5 set to be updated --> Finished Dependency Resolution Dependencies Resolved ================================================================================ Package Arch Version Repository Size ================================================================================ Installing: denyhosts noarch 2.6-5.el5 epel 98 k Transaction Summary ================================================================================ Install 1 Package(s) Upgrade 0 Package(s) Total download size: 98 k Is this ok [y/N]: y Downloading Packages: denyhosts-2.6-5.el5.noarch.rpm | 98 kB 00:00 Running rpm_check_debug Running Transaction Test Finished Transaction Test Transaction Test Succeeded Running Transaction Installing : denyhosts 1/1 Installed: denyhosts.noarch 0:2.6-5.el5 Complete! |
DenyHostsの設定ファイル /etc/denyhosts.confを編集します。今回は
・ブロックしたIPは自動削除しない
・rootでアクセスしてきたIPは1回でブロック
・存在しないユーザーで失敗すると1回でブロック
・存在するユーザーで3回失敗するとブロック
・新たにブロックが発生したらメールで管理者に通知
Defaultの/etc/denyhosts.conf
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############ THESE SETTINGS ARE REQUIRED ############ ######################################################################## # # SECURE_LOG: the log file that contains sshd logging info # if you are not sure, grep "sshd:" /var/log/* # # The file to process can be overridden with the --file command line # argument # # Redhat or Fedora Core: SECURE_LOG = /var/log/secure # # Mandrake, FreeBSD or OpenBSD: #SECURE_LOG = /var/log/auth.log # # SuSE: #SECURE_LOG = /var/log/messages # # Mac OS X (v10.4 or greater - # also refer to: http://www.denyhosts.net/faq.html#macos #SECURE_LOG = /private/var/log/asl.log # # Mac OS X (v10.3 or earlier): #SECURE_LOG=/private/var/log/system.log # ######################################################################## ######################################################################## # # HOSTS_DENY: the file which contains restricted host access information # # Most operating systems: HOSTS_DENY = /etc/hosts.deny # # Some BSD (FreeBSD) Unixes: #HOSTS_DENY = /etc/hosts.allow # # Another possibility (also see the next option): #HOSTS_DENY = /etc/hosts.evil ####################################################################### ######################################################################## # # PURGE_DENY: removed HOSTS_DENY entries that are older than this time # when DenyHosts is invoked with the --purge flag # # format is: i[dhwmy] # Where 'i' is an integer (eg. 7) # 'm' = minutes # 'h' = hours # 'd' = days # 'w' = weeks # 'y' = years # # never purge: #PURGE_DENY = # # purge entries older than 1 week #PURGE_DENY = 1w # # purge entries older than 5 days #PURGE_DENY = 5d # # For the default Fedora Extras install, we want timestamping but no # expiration (at least by default) so this is deliberately set high. # Adjust to taste. PURGE_DENY = 4w ####################################################################### ####################################################################### # # PURGE_THRESHOLD: defines the maximum times a host will be purged. # Once this value has been exceeded then this host will not be purged. # Setting this parameter to 0 (the default) disables this feature. # # default: a denied host can be purged/re-added indefinitely #PURGE_THRESHOLD = 0 # # a denied host will be purged at most 2 times. #PURGE_THRESHOLD = 2 # ####################################################################### ####################################################################### # # BLOCK_SERVICE: the service name that should be blocked in HOSTS_DENY # # man 5 hosts_access for details # # eg. sshd: 127.0.0.1 # will block sshd logins from 127.0.0.1 # # To block all services for the offending host: #BLOCK_SERVICE = ALL # To block only sshd: BLOCK_SERVICE = sshd # To only record the offending host and nothing else (if using # an auxilary file to list the hosts). Refer to: # http://denyhosts.sourceforge.net/faq.html#aux #BLOCK_SERVICE = # ####################################################################### ####################################################################### # # DENY_THRESHOLD_INVALID: block each host after the number of failed login # attempts has exceeded this value. This value applies to invalid # user login attempts (eg. non-existent user accounts) # DENY_THRESHOLD_INVALID = 5 # ####################################################################### ####################################################################### # # DENY_THRESHOLD_VALID: block each host after the number of failed # login attempts has exceeded this value. This value applies to valid # user login attempts (eg. user accounts that exist in /etc/passwd) except # for the "root" user # DENY_THRESHOLD_VALID = 10 # ####################################################################### ####################################################################### # # DENY_THRESHOLD_ROOT: block each host after the number of failed # login attempts has exceeded this value. This value applies to # "root" user login attempts only. # DENY_THRESHOLD_ROOT = 1 # ####################################################################### ####################################################################### # # DENY_THRESHOLD_RESTRICTED: block each host after the number of failed # login attempts has exceeded this value. This value applies to # usernames that appear in the WORK_DIR/restricted-usernames file only. # DENY_THRESHOLD_RESTRICTED = 1 # ####################################################################### ####################################################################### # # WORK_DIR: the path that DenyHosts will use for writing data to # (it will be created if it does not already exist). # # Note: it is recommended that you use an absolute pathname # for this value (eg. /home/foo/denyhosts/data) # WORK_DIR = /var/lib/denyhosts # ####################################################################### ####################################################################### # # SUSPICIOUS_LOGIN_REPORT_ALLOWED_HOSTS # # SUSPICIOUS_LOGIN_REPORT_ALLOWED_HOSTS=YES|NO # If set to YES, if a suspicious login attempt results from an allowed-host # then it is considered suspicious. If this is NO, then suspicious logins # from allowed-hosts will not be reported. All suspicious logins from # ip addresses that are not in allowed-hosts will always be reported. # SUSPICIOUS_LOGIN_REPORT_ALLOWED_HOSTS=YES ###################################################################### ###################################################################### # # HOSTNAME_LOOKUP # # HOSTNAME_LOOKUP=YES|NO # If set to YES, for each IP address that is reported by Denyhosts, # the corresponding hostname will be looked up and reported as well # (if available). # HOSTNAME_LOOKUP=YES # ###################################################################### ###################################################################### # # LOCK_FILE # # LOCK_FILE=/path/denyhosts # If this file exists when DenyHosts is run, then DenyHosts will exit # immediately. Otherwise, this file will be created upon invocation # and deleted upon exit. This ensures that only one instance is # running at a time. # # Redhat/Fedora: LOCK_FILE = /var/lock/subsys/denyhosts # # Debian #LOCK_FILE = /var/run/denyhosts.pid # # Misc #LOCK_FILE = /tmp/denyhosts.lock # ###################################################################### ############ THESE SETTINGS ARE OPTIONAL ############ ####################################################################### # # ADMIN_EMAIL: if you would like to receive emails regarding newly # restricted hosts and suspicious logins, set this address to # match your email address. If you do not want to receive these reports # leave this field blank (or run with the --noemail option) # # Multiple email addresses can be delimited by a comma, eg: # ADMIN_EMAIL = foo@bar.com, bar@foo.com, etc@foobar.com # ADMIN_EMAIL = root # ####################################################################### ####################################################################### # # SMTP_HOST and SMTP_PORT: if DenyHosts is configured to email # reports (see ADMIN_EMAIL) then these settings specify the # email server address (SMTP_HOST) and the server port (SMTP_PORT) # # SMTP_HOST = localhost SMTP_PORT = 25 # ####################################################################### ####################################################################### # # SMTP_USERNAME and SMTP_PASSWORD: set these parameters if your # smtp email server requires authentication # #SMTP_USERNAME=foo #SMTP_PASSWORD=bar # ###################################################################### ####################################################################### # # SMTP_FROM: you can specify the "From:" address in messages sent # from DenyHosts when it reports thwarted abuse attempts # SMTP_FROM = DenyHosts <nobody@localhost> # ####################################################################### ####################################################################### # # SMTP_SUBJECT: you can specify the "Subject:" of messages sent # by DenyHosts when it reports thwarted abuse attempts SMTP_SUBJECT = DenyHosts Report from $[HOSTNAME] # ###################################################################### ###################################################################### # # SMTP_DATE_FORMAT: specifies the format used for the "Date:" header # when sending email messages. # # for possible values for this parameter refer to: man strftime # # the default: # #SMTP_DATE_FORMAT = %a, %d %b %Y %H:%M:%S %z # ###################################################################### ###################################################################### # # SYSLOG_REPORT # # SYSLOG_REPORT=YES|NO # If set to yes, when denied hosts are recorded the report data # will be sent to syslog (syslog must be present on your system). # The default is: NO # #SYSLOG_REPORT=NO # #SYSLOG_REPORT=YES # ###################################################################### ###################################################################### # # ALLOWED_HOSTS_HOSTNAME_LOOKUP # # ALLOWED_HOSTS_HOSTNAME_LOOKUP=YES|NO # If set to YES, for each entry in the WORK_DIR/allowed-hosts file, # the hostname will be looked up. If your versions of tcp_wrappers # and sshd sometimes log hostnames in addition to ip addresses # then you may wish to specify this option. # #ALLOWED_HOSTS_HOSTNAME_LOOKUP=NO # ###################################################################### ###################################################################### # # AGE_RESET_VALID: Specifies the period of time between failed login # attempts that, when exceeded will result in the failed count for # this host to be reset to 0. This value applies to login attempts # to all valid users (those within /etc/passwd) with the # exception of root. If not defined, this count will never # be reset. # # See the comments in the PURGE_DENY section (above) # for details on specifying this value or for complete details # refer to: http://denyhosts.sourceforge.net/faq.html#timespec # AGE_RESET_VALID=5d # ###################################################################### ###################################################################### # # AGE_RESET_ROOT: Specifies the period of time between failed login # attempts that, when exceeded will result in the failed count for # this host to be reset to 0. This value applies to all login # attempts to the "root" user account. If not defined, # this count will never be reset. # # See the comments in the PURGE_DENY section (above) # for details on specifying this value or for complete details # refer to: http://denyhosts.sourceforge.net/faq.html#timespec # AGE_RESET_ROOT=25d # ###################################################################### ###################################################################### # # AGE_RESET_RESTRICTED: Specifies the period of time between failed login # attempts that, when exceeded will result in the failed count for # this host to be reset to 0. This value applies to all login # attempts to entries found in the WORK_DIR/restricted-usernames file. # If not defined, the count will never be reset. # # See the comments in the PURGE_DENY section (above) # for details on specifying this value or for complete details # refer to: http://denyhosts.sourceforge.net/faq.html#timespec # AGE_RESET_RESTRICTED=25d # ###################################################################### ###################################################################### # # AGE_RESET_INVALID: Specifies the period of time between failed login # attempts that, when exceeded will result in the failed count for # this host to be reset to 0. This value applies to login attempts # made to any invalid username (those that do not appear # in /etc/passwd). If not defined, count will never be reset. # # See the comments in the PURGE_DENY section (above) # for details on specifying this value or for complete details # refer to: http://denyhosts.sourceforge.net/faq.html#timespec # AGE_RESET_INVALID=10d # ###################################################################### ###################################################################### # # RESET_ON_SUCCESS: If this parameter is set to "yes" then the # failed count for the respective ip address will be reset to 0 # if the login is successful. # # The default is RESET_ON_SUCCESS = no # #RESET_ON_SUCCESS = yes # ##################################################################### ###################################################################### # # PLUGIN_DENY: If set, this value should point to an executable # program that will be invoked when a host is added to the # HOSTS_DENY file. This executable will be passed the host # that will be added as it's only argument. # #PLUGIN_DENY=/usr/bin/true # ###################################################################### ###################################################################### # # PLUGIN_PURGE: If set, this value should point to an executable # program that will be invoked when a host is removed from the # HOSTS_DENY file. This executable will be passed the host # that is to be purged as it's only argument. # #PLUGIN_PURGE=/usr/bin/true # ###################################################################### ###################################################################### # # USERDEF_FAILED_ENTRY_REGEX: if set, this value should contain # a regular expression that can be used to identify additional # hackers for your particular ssh configuration. This functionality # extends the built-in regular expressions that DenyHosts uses. # This parameter can be specified multiple times. # See this faq entry for more details: # http://denyhosts.sf.net/faq.html#userdef_regex # #USERDEF_FAILED_ENTRY_REGEX= # # ###################################################################### ######### THESE SETTINGS ARE SPECIFIC TO DAEMON MODE ########## ####################################################################### # # DAEMON_LOG: when DenyHosts is run in daemon mode (--daemon flag) # this is the logfile that DenyHosts uses to report it's status. # To disable logging, leave blank. (default is: /var/log/denyhosts) # DAEMON_LOG = /var/log/denyhosts # # disable logging: #DAEMON_LOG = # ###################################################################### ####################################################################### # # DAEMON_LOG_TIME_FORMAT: when DenyHosts is run in daemon mode # (--daemon flag) this specifies the timestamp format of # the DAEMON_LOG messages (default is the ISO8061 format: # ie. 2005-07-22 10:38:01,745) # # for possible values for this parameter refer to: man strftime # # Jan 1 13:05:59 #DAEMON_LOG_TIME_FORMAT = %b %d %H:%M:%S # # Jan 1 01:05:59 #DAEMON_LOG_TIME_FORMAT = %b %d %I:%M:%S # ###################################################################### ####################################################################### # # DAEMON_LOG_MESSAGE_FORMAT: when DenyHosts is run in daemon mode # (--daemon flag) this specifies the message format of each logged # entry. By default the following format is used: # # %(asctime)s - %(name)-12s: %(levelname)-8s %(message)s # # Where the "%(asctime)s" portion is expanded to the format # defined by DAEMON_LOG_TIME_FORMAT # # This string is passed to python's logging.Formatter contstuctor. # For details on the possible format types please refer to: # http://docs.python.org/lib/node357.html # # This is the default: #DAEMON_LOG_MESSAGE_FORMAT = %(asctime)s - %(name)-12s: %(levelname)-8s %(message)s # # ###################################################################### ####################################################################### # # DAEMON_SLEEP: when DenyHosts is run in daemon mode (--daemon flag) # this is the amount of time DenyHosts will sleep between polling # the SECURE_LOG. See the comments in the PURGE_DENY section (above) # for details on specifying this value or for complete details # refer to: http://denyhosts.sourceforge.net/faq.html#timespec # # DAEMON_SLEEP = 30s # ####################################################################### ####################################################################### # # DAEMON_PURGE: How often should DenyHosts, when run in daemon mode, # run the purge mechanism to expire old entries in HOSTS_DENY # This has no effect if PURGE_DENY is blank. # DAEMON_PURGE = 1h # ####################################################################### ######### THESE SETTINGS ARE SPECIFIC TO ########## ######### DAEMON SYNCHRONIZATION ########## ####################################################################### # # Synchronization mode allows the DenyHosts daemon the ability # to periodically send and receive denied host data such that # DenyHosts daemons worldwide can automatically inform one # another regarding banned hosts. This mode is disabled by # default, you must uncomment SYNC_SERVER to enable this mode. # # for more information, please refer to: # http:/denyhosts.sourceforge.net/faq.html#sync # ####################################################################### ####################################################################### # # SYNC_SERVER: The central server that communicates with DenyHost # daemons. Currently, denyhosts.net is the only available server # however, in the future, it may be possible for organizations to # install their own server for internal network synchronization # # To disable synchronization (the default), do nothing. # # To enable synchronization, you must uncomment the following line: #SYNC_SERVER = http://xmlrpc.denyhosts.net:9911 # ####################################################################### ####################################################################### # # SYNC_INTERVAL: the interval of time to perform synchronizations if # SYNC_SERVER has been uncommented. The default is 1 hour. # #SYNC_INTERVAL = 1h # ####################################################################### ####################################################################### # # SYNC_UPLOAD: allow your DenyHosts daemon to transmit hosts that have # been denied? This option only applies if SYNC_SERVER has # been uncommented. # The default is SYNC_UPLOAD = yes # #SYNC_UPLOAD = no #SYNC_UPLOAD = yes # ####################################################################### ####################################################################### # # SYNC_DOWNLOAD: allow your DenyHosts daemon to receive hosts that have # been denied by others? This option only applies if SYNC_SERVER has # been uncommented. # The default is SYNC_DOWNLOAD = yes # #SYNC_DOWNLOAD = no #SYNC_DOWNLOAD = yes # # # ####################################################################### ####################################################################### # # SYNC_DOWNLOAD_THRESHOLD: If SYNC_DOWNLOAD is enabled this parameter # filters the returned hosts to those that have been blocked this many # times by others. That is, if set to 1, then if a single DenyHosts # server has denied an ip address then you will receive the denied host. # # See also SYNC_DOWNLOAD_RESILIENCY # #SYNC_DOWNLOAD_THRESHOLD = 10 # # The default is SYNC_DOWNLOAD_THRESHOLD = 3 # #SYNC_DOWNLOAD_THRESHOLD = 3 # ####################################################################### ####################################################################### # # SYNC_DOWNLOAD_RESILIENCY: If SYNC_DOWNLOAD is enabled then the # value specified for this option limits the downloaded data # to this resiliency period or greater. # # Resiliency is defined as the timespan between a hackers first known # attack and it's most recent attack. Example: # # If the centralized denyhosts.net server records an attack at 2 PM # and then again at 5 PM, specifying a SYNC_DOWNLOAD_RESILIENCY = 4h # will not download this ip address. # # However, if the attacker is recorded again at 6:15 PM then the # ip address will be downloaded by your DenyHosts instance. # # This value is used in conjunction with the SYNC_DOWNLOAD_THRESHOLD # and only hosts that satisfy both values will be downloaded. # This value has no effect if SYNC_DOWNLOAD_THRESHOLD = 1 # # The default is SYNC_DOWNLOAD_RESILIENCY = 5h (5 hours) # # Only obtain hackers that have been at it for 2 days or more: #SYNC_DOWNLOAD_RESILIENCY = 2d # # Only obtain hackers that have been at it for 5 hours or more: #SYNC_DOWNLOAD_RESILIENCY = 5h # ####################################################################### |
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[root@host1 ~]# chkconfig --list | grep denyhosts denyhosts 0:off 1:off 2:off 3:off 4:off 5:off 6:off [root@host1 ~]# chkconfig denyhosts on [root@host1 ~]# chkconfig --list | grep denyhosts denyhosts 0:off 1:off 2:on 3:on 4:on 5:on 6:off |
sshを常に許可するIPを/etc/hosts.allowに記述します
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[root@host1 ~]# vi /etc/hosts.allow sshd: 192.168.200. |
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[root@host1 ~]# /etc/init.d/denyhosts start starting DenyHosts: /usr/bin/env python /usr/bin/denyhosts.py --daemon --config=/etc/denyhosts.conf [root@host1 ~]# ps ax | grep denyhosts 11404 ? S 0:00 python /usr/bin/denyhosts.py --daemon --config=/etc/denyhosts.conf 11407 pts/0 S+ 0:00 grep denyhosts |
開始されると /var/log/secureを調べて設定した条件に合ったIPをブロックするために/etc/hosts.denyに追加されます。今回は15個のIPが登録され管理者にメールが届きました
しばらくこれで様子をみます
ちなみにログは/var/log/denyhostsでlogrotateもインストール時に設定されています