lisaac: 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/lisaac - from package: lisaac

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

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