sylfilter: 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/sylfilter - from package: sylfilter

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

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