Does the Debian Security team check every new package in Debian?
No, the Debian security team does not check every new package and neither is there an automatic (lintian) check in order to detect malicious new packages, since those checks are rather impossible to detect automatically. Maintainers, however, are fully responsible for the software that is introduced in Debian and no software is introduced that is not first signed by an authorised developers. They are in charge of analysing the software they maintain and are security-aware.
