Abstract-- The TCP/IP suite, the basis for today's Internet, lacks even the most basic mechanisms of authentication. As usage of the Internet increases, its scarcity of built-in security becomes more and more problematic. This paper describes serious attacks against IP control and management protocols with an accent on the ICMP protocol, as well as some of the well-known vulnerabilities of the inter-domain routing protocols. All the presented attacks have at least one common feature: they exploit intrinsic IP security flaws. The paper also discusses various solutions to these security breaches, including the use of IPsec, which currently offers cryptographic security services for the Internet infrastructure. Keywords--Denial of Service, authentication, IP Security, routing security, public key infrastructure.