The lecture course "Internet Security II - Weaknesses and Targets" is based on the lecture course "Internet Security I - Internet Technology" and gives a detailed introduction into problems concerning Internet and Intranet security. After starting with a some remarks on risk analysis and computer crimes, security weaknesses and targets are discussed in detail. Beside others the following topics are discussed in detail: human factor and technical failures, attacks on accounts and passwords, attacks on Internet protocol, misuse of design and programming errors, weaknesses in common operating systems, targets in the WWW, and viruses. The lecture course concludes with a discussion of possibilities to detect attacks and intrusions, and ethical issuses.