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Home FinalTrace 2025 Phantom Fingerprints
Writeup
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Phantom Fingerprints

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  • Category: [Forensics]
  • Author: [Htarizzs]

Challenge Description

[Use the provided netcat service and query logs to identify and analyze the activity of a phantom user whose fingerprints appear in the device logs, but who does not correspond to any registered account. Find and submit their session’s flag.]

Solution

Initial Analysis

  • Reconnaissance Begin by connecting to the provided netcat service (e.g., nc challenge.host 1337). Review the welcome message, available commands (usually presented with a help command), and the structure of returned data.
  • Information Gathering Use commands like show logs, query user , query fingerprint , etc., to get an inventory of normal and phantom records, paying attention to any IDs, timestamps, or unusual entries.

Tools Used

  • [netcat (nc)]
  • [python3 (py)]

Step-by-Step Solution

Step 1: [Connect & Explore]

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2
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nc localhost 1337
help
show logs

[The terminal is bought up, which will only work with specific commands which are specified in help.]

Step 2: [Find the phantom user]

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query user 0x9999
query fingerprint fp9999

[Phantom(Unknown) user is found out, and try inspecting their fingerprint to get the flag in base64 format]

Step 3: [Decode the base64 string]

Decoding the base64 string obtained will give the flag

Flag

1
CYS{ph4n7om_v3n0m}

Flag

CYS{ph4n7om_v3n0m}
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