threat hunting | payload analysis with ngrep - part 3

we found a suspicious ip pair lets say:

192.168.99.51 to 104.248.234.238

lets analyze the payloads in these sessions. 

ngrep -q -I trace1.pcap host 192.168.99.51 and host 104.248.234.238 | head -20

the GET request url is weird. windows 7 version is weird and java 1.7 version is also weired. host is showing ip address which is wrong. host field should always be FQDN. 200 OK means server is happy to give you what you have asked for.

cat http.log | zeek-cut id.orig_h id.resp_h user_agent | grep 192.168.99.51 | sort | uniq | cut -f 3 | sort | uniq -c | sort -rn

 

1st sorting is when they are same then they are arranged all together

uniq --> say i am connecting same destinaiton ip 50 times. so instead of 50 lines make it as 1 line. then connecting another 20 same destination ip's. collapse them again in a single line.

then we are again sorting it. 

uniq -c --> say my system is communicating 50 different ip address. it will then show the count number. 

 

so from the above image we can see that, 29 different ip addresses Microsoft_WNS/10.0 host communicated. 10 means windows 10. 

 

Now what data we are sending? is this the only url we send to this host? we could eyeball it because it is a long garbage string so if some letter change in between we would not be able to catch it. zeek stores in this type of data in its http.log file. lets use this log to identify all of the url's requested from this host to external host. 

cat http.log | zeek-cut id.orig_h id.resp_h uri | grep 104.248.234.238 | sort | uniq -c | sort -rn 

this string says no data is being transferred but this a c2 channel definitely. if any data is being transferred then longer string we would have seen. this simply says, do you have anything for me to do? C2 says no go back to sleep. but we should definitely investigate this host. 

search rmvk30g on google. you will see fiesta ek malware doing this.  

 

Avi