Add this to your sources.lst:
Then you need to get the key and add it to apt:
Then just
deb http://download.opensuse.org/repositories/security:/OpenVAS:/UNSTABLE:/v4/xUbuntu_10.10/ ./
Then you need to get the key and add it to apt:
wget http://download.opensuse.org/repositories/security:/OpenVAS:/UNSTABLE:/v4/xUbuntu_10.10/Release.key
apt-key add Release.key
rm Release.key
Then just
apt-get update