sniffit: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/sbin/sniffit - from package: sniffit

You may install the required package with command apt-get install {package}

Error in other languages:
sniffit: bevel nie gevind nie
sniffit: comandă negăsită
sniffit: comando não encontrado
sniffit: commande introuvable
sniffit: command not found
sniffit: käsku ei ole
sniffit: không tìm thấy lệnh
sniffit: komanda nerasta
sniffit: Kommando nicht gefunden.
sniffit: kommandot finns inte
sniffit: komut yok
sniffit: nie znaleziono polecenia
sniffit: níor aimsíodh an t-ordú
sniffit: no se encontró la orden
sniffit: no s'ha trobat l'ordre
sniffit: opdracht niet gevonden
sniffit: parancs nem található
sniffit: perintah tidak ditemukan
sniffit: príkaz nenájdený
sniffit: příkaz nenalezen
sniffit: команда не найдена
sniffit: командата не е открита
sniffit: 命令找不到
sniffit: コマンドが見つかりません