Thoughts, stories and ideas.

Have you encountered with DDoS Trojan attack?

It’s a familiar issue to all SysAdmins, when we work on DDoS attack. Normally, the top command shows a suspicious process with a random name like, Xdrgwdjd, jjiiyaykzg etc or some system commands like ls, ifconfig, pwd, ping, awk, telnet etc.

When we kill that task another random process is being generated immediately.

Steps to fixing the attack :
———————

1) List the files under hourly cron. If you can see any .sh file, please open it.

[email protected]# ls -la /etc/cron.hourly/

++++++++++
# ls /etc/cron.hourly/
freshclam gcc.sh
++++++++++

2) If the .sh file is showing similar data as shown below, then it’s a Virus program!!

[email protected]# cat /etc/cron.hourly/gcc.sh

++++++++++
cat /etc/cron.hourly/gcc.sh
#! / Bin / sh
PATH = / bin: / sbin: / usr / bin: / usr / sbin: / usr / local / bin: / usr / local / sbin: / usr / X11R6 / bin
for i in `cat / proc / net / dev | grep: | awk -F: {‘print $ 1’}`; do ifconfig $ i up & done
cp /lib/libudev.so /lib/libudev.so.6
/lib/libudev.so.6
++++++++++

3) Now, please don’t be hurry! Stay calm and easy

# Do not delete gcc.sh or do not remove the crontab. If you do delete or remove it, then another process will generate immediately.

# You can either remove the culprit script or disable it. [ I prefer to disable it to show the proof to the customer ]

[email protected]# rm -f /etc/cron.hourly/gcc.sh;

OR

[email protected] # chmod 0 /etc/cron.hourly/gcc.sh; chattr +ia /etc/cron.hourly/gcc.sh; chattr + i /etc/crontab

4) Use top command to view virus or malicious file ( Eg :”mtyxkeaofa” ) PID is 16621, do not directly kill the program, otherwise it will again produce, but to stop its operation use the below command.

———————————-
[email protected] # kill -STOP 16621

# Delete files within /etc/init.d. or disable it [ I prefer to disable it to show the proof to the customer ]

[email protected]# find /etc -name '* mtyxkeaofa *' | xargs rm -f

OR

chmod 0 /usr/bin/mtyxkeaofa;
chmod 0 /etc/init.d/mtyxkeaofa;
chattr +ia /usr/bin/mtyxkeaofa;
chattr +ia /etc/init.d/mtyxkeaofa;
———————————-

6) Delete /usr/bin inside archives.

[email protected]# rm -f /usr/bin/mtyxkeaofa;

7) Check /usr/bin archives recent changes, the virus can also be deleted if the other suspect is the same directory.

[email protected]# ls -lt /usr/bin | head

8) Now kill the malicious program, it will not produce.

[email protected]# pkill mtyxkeaofa

9) Remove the virus body.

[email protected]# rm -f /lib/libudev.so

This trojan is also know as Chinese Chicken Multiplatform DoS botnets Trojan, Unix – Trojan.DDoS_XOR-1, Embedded rootkit,

Note :

~ If you are unable to find .sh file, you may please install ClamAV, RKHunter and check logs/report to find the suspicious/malicious