You can also use gdb to list the functions of the program and then disassemble and inspect certain aspects of that function.
Code:
(gdb) info functions
All defined functions:
Non-debugging symbols:
0x080485d0 _init
0x080485f8 close@plt
0x08048608 select@plt
0x08048618 bcopy@plt
0x08048628 system@plt
0x08048638 puts@plt
0x08048648 getpeername@plt
0x08048658 fgets@plt
0x08048668 strstr@plt
0x08048678 __libc_start_main@plt
0x08048688 printf@plt
0x08048698 getuid@plt
0x080486a8 fcntl@plt
0x080486b8 fclose@plt
0x080486c8 snprintf@plt
0x080486d8 gethostbyname@plt
0x080486e8 exit@plt
0x080486f8 send@plt
0x08048708 htons@plt
0x08048718 memset@plt
---Type <return> to continue, or q <return> to quit---
0x08048728 connect@plt
0x08048738 fopen@plt
0x08048748 recv@plt
0x08048758 socket@plt
0x08048768 __gmon_start__@plt
0x08048780 _start
0x080487a4 call_gmon_start
0x080487d0 __do_global_dtors_aux
0x08048800 frame_dummy
0x08048824 promosi
0x08048850 imapattack
0x080488a7 apacheattack
0x08048ac8 ctimeout
0x08048ca0 bannertest
0x08048ee5 main
0x08049104 __libc_csu_fini
0x0804910c __libc_csu_init
0x08049160 __do_global_ctors_aux
0x0804918c _fini
(gdb) disass fopen
No symbol table is loaded. Use the "file" command.
(gdb) disass fopen\@plt
No symbol table is loaded. Use the "file" command.
(gdb) disass promosi
Dump of assembler code for function promosi:
0x08048824 <promosi+0>: push %ebp
0x08048825 <promosi+1>: mov %esp,%ebp
0x08048827 <promosi+3>: sub $0x8,%esp
0x0804882a <promosi+6>: movl $0x80491b4,(%esp)
0x08048831 <promosi+13>: call 0x8048638 <puts@plt>
0x08048836 <promosi+18>: movl $0x80491d8,(%esp)
0x0804883d <promosi+25>: call 0x8048638 <puts@plt>
0x08048842 <promosi+30>: movl $0x8049218,(%esp)
0x08048849 <promosi+37>: call 0x8048638 <puts@plt>
0x0804884e <promosi+42>: leave
0x0804884f <promosi+43>: ret
End of assembler dump.
(gdb) x/s 0x80491d8
0x80491d8 <__dso_handle+40>: "Apache mod_j/k Fedora Core 6/5 - Debian 3.1 - FreeBSD 5.4REL"
(gdb) x/s 0x8049218
0x8049218 <__dso_handle+104>: "Gnu mailutils imap4d Fedora Core 6 - Fedora Core 3\n\n"
(gdb)