The use of so many computers makes it difficult to know where the attack is coming from or who is coordinating it. In many cases, users are unaware of common security vulnerabilities that allow their machines to be captured. Unlike other cracker tricks, denial of service attacks do not penetrate the targeted computers or steal sensitive data. By denying access to popular sites, the crackers cost both individuals and companies time and money. Decisions are delayed, revenue is lost, money and engineering time is spent to rebuff the attack and restore site security.
Software can detect attacks by identifying the repetitive incoming data.
Traffic can be switched around in response, diminishing the impact. However, crackers keep developing new automated tools. The recipient knows exactly who sent the mail, and gets useful contact information. Adding a signature. Use a plain text editor like Windows Notepad or Mac's Simple Text to create your signature.