attack: 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/bin/attack - from package: ladr4-apps

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

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