Network traffic research

Especially for future students of the course “Network engineer. Basic ” our expert - Alexander Kolesnikov prepared an interesting author's material.



We also invite you to take part in an open online lesson on the topic “STP. What? What for? Why?" ... The participants of the lesson, together with an expert, will review the STP protocol, analyze the logic of its operation, and analyze its advantages and disadvantages.

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This article will tell you how you can work with network traffic. Using the example of several dumps of network traffic, the work of several useful tools will be analyzed, and approaches to extracting and collecting information from traffic are shown.

Instrumentation and research methodology

We will use the following software to parse the traffic:

• wireshark ;

  
  
  
  
  

• tshark ;

  
  
  
  
  

, . tshark



wireshark



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Disclamer: CTF, .

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:

1.pcap(9cd84b46fee506dae818ecdca76607d1)



. — , "FLAG-???????????"



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WireShark (, , tshark



. WireShark ). WireShrak "Statistics->Endpoints":

8 IP , . . "Statistics->Protocol Hierarchy":

, — http. pcap



body



. tshark



. :

```  tshark -r ./1.pcap -Y http -Tfields -e http.file_data | grep "FLAG"```
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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— 2.pcap (9a67e1fb9e529b7acfc6e91db6e1b092)



. . :

13 — . :

, . tcp . udp - :

``` tshark -r ./2.pcap -Y 'dns' ```
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, dns, :

ip , - . :

```tshark -r ./2.pcap -Y '!icmp.code && dns.qry.name contains 192.168' -Tfields -e 
dns.qry.name | tr '.' ' ' |awk '{print $1}' |xxd -r```
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

base64



, :

``` base64 -D <<< 
"VGhpcyBpcyBhIHNlY3JldCB0Y3JldCB0cmFuc21pdHRlZCB0aHJvdWdoaHJvdWdoIGRucyBxdWVyeSA6KSBGTEFHKSBGTEFHLUZUNDdjTVgyNnBXeUZTSTZSeUZTSTZSUFdhU3I1WVJ3"```
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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3.pcap(0e66830db52ad51971d40c77fa5b02c0)



. :

, , — . http.

``` tshark -r ./3.pcap -Y http```
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, http "flag.zip" "secret.txt". Wireshark :

, flag.zip



WireShark. , — Raw :

:

, , . , , tcp, :

:

```python 
 data = []
 with open('dump') as f:
     data = f.read()
     
with open('tesst.zip','w') as w:
    w.write(data[1010788:])
```
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

:

``` 7z x ./test.zip ```
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, , flag.txt

. , 4.pcap(604bbac867a6e197972230019fb34b2e)



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