我有几台 Debian lenny 电脑。其中两台有几乎相同的 sources.list 文件。我在这两台电脑上都定期进行更新/安全升级。在一台电脑上，更新/安全升级总是很顺利。在另一台电脑上，我经常得到以下信息：
sudo aptitude safe-upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Reading extended state information
Initializing package states... Done
Reading task descriptions... Done
The following packages will be upgraded:
krb5-clients krb5-ftpd krb5-rsh-server krb5-telnetd krb5-user libimlib2 libkadm55 libkrb53 libpng12-0 libpulse0 xpdf xpdf-common
xpdf-reader
13 packages upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 2906kB of archives. After unpacking 36.9kB will be used.
Do you want to continue? [Y/n/?]
WARNING: untrusted versions of the following packages will be installed!
Untrusted packages could compromise your system's security.
You should only proceed with the installation if you are certain that
this is what you want to do.
krb5-rsh-server krb5-user krb5-ftpd krb5-clients libkrb53 xpdf-reader libpng12-0 libkadm55 xpdf libpulse0 libimlib2 krb5-telnetd
xpdf-common
Do you want to ignore this warning and proceed anyway?
To continue, enter "Yes"; to abort, enter "No": no
Abort.
不用说，我没有继续。发生了什么事？我该如何解决？这些是此计算机的 sources.list 中的非注释行：
deb ftp://ftp.debian.org/debian/ lenny main contrib non-free
deb-src ftp://ftp.debian.org/debian/ lenny main contrib
deb http://security.debian.org/ lenny/updates main contrib non-free
谢谢。
答案1
wheezy 中的 Kstars 未签名，其他很多东西也是如此。要么是存储库被盗用，要么是有人疏忽了责任。