데비안 8에 ufw를 설치할 수 없습니다

방금 새 Debian 8을 설치했는데 설치하려고 하면 다음과 같이 ufw반환됩니다.

# apt-get install ufw
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package ufw is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'ufw' has no installation candidate

이 내 꺼야:/etc/apt/sources.list

deb http://security.debian.org/ jessie/updates main contrib
deb-src http://security.debian.org/ jessie/updates main contrib

clamav를 설치하려고 해도 같은 일이 발생합니다.

해결책은 무엇입니까?