OverTheWire Bandit: Level 9 to Level 10

The Goal

Find the password in data.txt — stored in one of the few human-readable strings, preceded by several = characters.

What I Did

The level mentioned “human-readable strings” which immediately suggested the file wasn’t plain text. I checked the strings man page first, then ran it on the file:

bandit9@bandit:~$ strings data.txt

That printed a wall of readable text extracted from what was otherwise a binary file. Too much to read through manually. Since the level said the password was preceded by = signs, I piped the output into grep:

bandit9@bandit:~$ strings data.txt | grep "="

That filtered the output down to only lines containing =, one of which had several = signs followed by the password.

What Was Actually Happening

data.txt is a binary file — not plain text. Running cat on it would flood the terminal with garbage characters. The file contains mostly non-printable binary data with a few human-readable strings embedded inside it.

strings scans a file and extracts sequences of printable characters above a minimum length (4 by default). It ignores everything else — all the binary noise — and outputs only the readable parts. This is how you pull text out of executables, compressed files, or any binary format.

grep "=" then filtered that output for lines containing =. Since the password was described as being preceded by multiple = characters, this narrowed the results immediately to the relevant line.

The pipe connects both — strings output flows directly into grep without touching disk.

Other Ways I Could Have Done It

strings with minimum length filter:

strings -n 10 data.txt | grep "="

-n 10 only extracts strings of 10 characters or longer, cutting out short fragments that add noise.

grep -a directly on the binary:

grep -a "===" data.txt

The -a flag forces grep to treat a binary file as text. Works but produces messier output with binary characters mixed in.

xxd for inspection:

xxd data.txt | grep "==="

xxd shows a hex dump with ASCII characters on the side. Useful for low-level inspection of binary content but much harder to read than strings.

strings | grep is the cleanest approach for this type of problem.

What I Learned

strings extracts readable text from binary files. Any time a file isn’t plain text — executables, compressed archives, unknown formats — strings is the first tool to reach for when you want to see what readable content is inside.

Binary files will break cat. Your terminal fills with garbage characters and sometimes gets into a broken state. Always check what type of file you’re dealing with using file before reading it.

Piping filters progressively. strings does the broad extraction, grep does the precise filtering. Each command does one thing. The pipe connects them.

Commands Used

Command	What it did
man strings	Checked what strings does before using it
strings data.txt	Extracted all human-readable text from the binary file
strings data.txt \| grep "="	Filtered output to lines containing = signs