BusyBox may contain many UNIX utilities, run busybox --list-full to check what GTFBins binaries are supported. Here some example.

Shell

It can be used to break out from restricted environments by spawning an interactive system shell.

busybox sh

File upload

It can exfiltrate files on the network.

Serve files in the local folder running an HTTP server.

LPORT=12345
busybox httpd -f -p $LPORT -h .

File write

It writes data to files, it may be used to do privileged writes or write files outside a restricted file system.

LFILE=file_to_write
busybox sh -c 'echo "DATA" > $LFILE'

File read

It reads data from files, it may be used to do privileged reads or disclose files outside a restricted file system.

LFILE=file_to_read
./busybox cat "$LFILE"

SUID

If the binary has the SUID bit set, it does not drop the elevated privileges and may be abused to access the file system, escalate or maintain privileged access as a SUID backdoor. If it is used to run sh -p, omit the -p argument on systems like Debian (<= Stretch) that allow the default sh shell to run with SUID privileges.

This example creates a local SUID copy of the binary and runs it to maintain elevated privileges. To interact with an existing SUID binary skip the first command and run the program using its original path.

It may drop the SUID privileges depending on the compilation flags and the runtime configuration.

sudo install -m =xs $(which busybox) .

./busybox sh

Sudo

If the binary is allowed to run as superuser by sudo, it does not drop the elevated privileges and may be used to access the file system, escalate or maintain privileged access.

sudo busybox sh