aka working with pcaps
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Some of the Forensics Challenges from Hacktoberfest CTF 2020.
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The amcache can be a pretty handy tool to help build out a timeline of execution during an investigation, and is always located in \%SystemRoot%\AppCompat\Programs\Amcache.hve what was the application
So the description for this challenge briefly explains what amcache is, and also gives a link to a file.
If you want more information on Amcache, this is a great link.
So upon research, I found RegRipper can be used to do this, however, there are plenty of other great tools out there. The one I decided to use for this challenge was AmCacheParser.
AmCacheParser runs on Windows and is basically a tool to analyse and "parse" Amcache. so the command we run this through the windows command prompt.
We run the above command in the AmcacheParser
folder. To break this down we run AmcacheParser.exe
taking the -f
argument which tells the tool which file to take as an input, we then specify the file given which was Amcache.hve
. We also need to give an output for the files, this is the --csv
part of the command and we specify the folder next. This will run the tool and the output will be in the file OutputFolder
, or whatever you chose to name it.
So as the above image shows, we now have a lot of Excel files to sort through, I first re-read the description to see what we needed and it led me to look in the 20201017155041_Amcache_UnassociatedFileEntries
entry, which looks a bit like this:
Once here i then used the find tool (CTRL + F
) to search for mpowers
which was the user given to us by the description. Below are the entries for mpowers
, more specifically from the full path column.
Full Path:
c:\users\mpowers\appdata\local\temp\d930e9b6-7d1b-4a5d-804e-ce667e431ff9\dismhost.exe
c:\users\mpowers\desktop\ftk imager\ftk imager.exe
c:\users\mpowers\downloads\python-3.7.0-amd64-webinstall.exe
c:\users\mpowers\appdata\local\temp\4{b04d01b2-0174-4ef5-8fb5-84584c0964f5}.be\python-3.7.0-amd64-webinstall.exe
c:\users\mpowers\appdata\local\temp\4{4a1d9cda-5382-4f04-b44d-51927f9c602a}.cr\python-3.7.0-amd64-webinstall.exe
c:\users\mpowers\desktop\sub-win-x64_104.148.109.124_5682_3262.exe
So as shown above, we have quite a lot of file paths. We were told to find what he installed, so I instantly looked deeper at the python install executables. It is very clear he installed Python
on the system so i tried the flag as flag{python}
and we scored the flag.
Writeup created by Chris Harris (@cjharris18)
Right so they started off easy. Opening up the pcap I used the http
display filter to show packets of this protocol:
Opening up the details for the first packet, we can see the full request URL
at http://www.sinotes.com/wp-content/themes/avada/picture4.png. I then ran wget
http://www.sinotes.com/wp-content/themes/avada/picture4.png
to download the file. As the brief suggests, this is not a png but rather a windows executable. Therefore renaming it to ecorp.exe
and running the command md5sum ecorp.exe
gives us the flag of flag{a95d24937acb3420ee94493db298b295}
.
Here, we need to use some display filters to refine our search. Firstly, we know it uses the same port as HTTPS. This is port 443. Secondly, We're talking about the malware and know that the infected client's ip is 192.168.1.91
from challenge 1. Putting this into a display filter would look like this:
Although there are quite a few packets, there are only so many different ips, so trying about 5 got me the correct answer, which was flag{213.136.94.177}
.
This was an interesting one. After some googling, I found out that Certificates are sent during tls handshakes, as TLS is used to encrypt HTTP traffic, making it HTTPS. The Display filter i needed to show these packets was tls.handshake.type == 11
.
As said in the brief, we need the packet from the source IP 37.205.9.252
. Therefore expaning this packet's details, then TLSv1.2 Record Layer: Handshake Protocol: Certificate
then Handshake Protocol: Certificate
then Certificates
then subject: rdnSequence (0)
finally gives us the LocalityName.
flag{Mogadishu}
By das :)
Simply opening it up in wireshark, we can see the flag-
flag{solut.exe}
All you need to do here is filter for dns
traffic. Because there weren't too many packets, I spotted the flag almost immediately and didn't have to filter further.
flag{solution.myddns.me}
Like the others, you can just filter for http
traffic and get the flag:
flag{205.185.125.104}
We're looking for a domain, so it must be a dns
query. Therefore filtering for DNS traffic and specifying the ip (10.0.0.163
as this is the infected client from part 1, and the infected client must've made the query) we can get the flag-
flag{vlcafxbdjtlvlcduwhga.com}
By das
We found some unusual activity coming from an employee's Windows 10 workstation at De Monne Financial. Our IT guy saved the memory dump to the file provided below. What was the PID of the program used
For this challenge, you get given a mem.raw
file. So initially this along with the title screams memory forensics and so the main program that comes to mind is Volatility, if unfamiliar with this tool, it can be best described as a memory forensics tool to help you look at memory captures of RAM. This tool should be automatically installed on Kali, but other distros should follow install instructions found on the GitHub page (linked above).
It is worth noting I used Volatility 2
in this writeup, the syntax for Volatility 3
is similar, just replace volatility
with vol3
it could also be worth noting that depending on your install, you might need to run it as volatility.py
So to start with you run the following command with a memdump/raw format, the imageinfo
plugin will provide basic information on the memory capture:
Breaking this command down we have the name of the program volatility
followed by -f
which tells volatility to take in the file mem.raw
, then as outlined above the imageinfo
plugin gives us basic information on the image. I then personally followed it with > raw_imageinfo.txt
just so I have it saved in a text file should i need it earlier. This is not essential, however i reccomend it, especially for when Volatility can have a lot of input, it also gives you the power of tools like grep
and awk
.
Then we take the profile, normally we take the first however it won't always work, luckily ,in this case, it was the first profile which is Win10x64_1734
.
We then run the following command as we were told we needed the PID
so automatically i decided to look at the processes, now this can be done with either the pstree
plugin or the pslist
plugin, the difference is mainly that pstree
gives us a more visual representation of which process was launched by which, whereas pslist
lists them all. I chose pstree
, the command is shown below:
Breaking this down, we have the volatility -f raw.mem
as I mentioned before which initialises Volatility along with specifying the file. The big difference here is that we now specify a profile as shown by the --profile=Win10x64_1734
part of our command, when we ran imageinfo
we took the profile and now we need to specify it to Volatility to run further plugins. The next part of our command is pstree
which as outlined above creates a tree of all processes on the system. I then also save this in a file again with > raw_pstree.txt
which helps me with things like grep but also means I only need to run this command once. Below is a shortened output for the sake of the writeup:
Now if we scroll down we see the below process:
I assumed this was the process as we know it was a Windows system from the challenge description. So for the flag, we simply took the PID
which was 3348
, which we then submitted as the flag in the form specified which was: flag{3348}
.
Writeup created by Chris Harris (cjharris).
Flags 1, 2, 3 and 4
SSHing in and running the command whoami
we see we're logged in as luciafer
.
Navigating to /home/luciafer/Documents
, I ran ls -alt
and the output was as follows:
Since luciafer
owns both these files, I can simply run cat flag1.txt
and cat .flag2.txt
to get the flags.
flag 1: flag{cb07e9d6086d50ee11c0d968f1e5c4bf1c89418c}
flag 2: flag{728ec98bfaa302b2dfc2f716d3de7869f3eadcbf}
After looking around, I found flag3.txt located at /home/spookyboi/Documents/flag3.txt
and flag4.txt at /root/flag4.txt
. Since luciafer doesn't have sufficient perms to read these files, I ran the command
find / -perm -u=s -type f 2>/dev/null
to find SUID files.
SUID is a special file permission for executable files, which enables other users to run the file with effective permissions of the file owner. This means we could privilege escalate to root or a higher privileged user, giving us perms to read the flag files.
This was the output:
The program ouija
jumped out to me, so i tried running it:
Excellent! it reads files in the /root
directory, meaning we simply go
We use the same program to get the flag from flag3.txt as so:
Note: as we start in the /root
directory, so must go back one (../
) to navigate to flag3.txt.
By das