The default is NO (turn signal handling on). By setting BEQUEATH_DETACH=YES, Oracle turns off its own signal handlers and pass all child processes over to the UNIX init process (pid = 1). The init process will take over responsibility to checks for "defunct" child processes and terminate them.
Instead of setting this parameter in the sqlnet.ora file, consider setting it as an environment variable before starting applications that use signal handlers that could interfere with SQL*Net. Example:
export BEQUEATH_DETACH=YES