telnet? nhung telnet cai gi? cong nao? nhieu thu lam, ftp, smtp, pop3, gopher, router, switch, ... cu tim thu mot cai mang nao do roi test thu ftp la 21, pop3 la 110, router thi tuy vao mang dat, co khi la 28, hoac cung co the la khac, switch cung vay, ... ma hoi de lam gi vay? tinh lam hacker a?
