cufilter: 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/cufilter - from package: libmail-checkuser-perl

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

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