Of course, it is not intended for users to play with as a way of learning more about Oracle data block internals. To that end it is protected by a password known only to trained Oracle support people. It does have a HELP facility, but that is only enough to remind users of the syntax. Anyone who does not already understand the data structures and their relationships, and who has not been trained in the use of BBED would hard pressed to make any use of it.
Hackers might use BBED to break into an Oracle database. Tools like BBED can be used to view data directly within their data block (bypassing the Oracle later), and because BBED writes directly the data block, BBED could be used by hackers to update a database without logging and auditing.
This paper titled "disassembling the Oracle data block" has complete instructions for installing and using BBED. This make command tells how to linkedit BBED:
Orafaq.com's Miladin Modrakovic has an article on Fixing" SYS for hacking purposes which uses bbed
make -f ins_rdbms.mk BBED=$ORACLE_HOME/bin/bbed $ORACLE_HOME/bin/bbed