Figure 11-6: Interactions in the simple Mail Transfer Protocol ( SMTP) Actor SMTP Command Comment The message. Multiple lines Of text. Ends with line Client When in the course Containing only a single Period <CRLF><CRLF> Server 250 OK Server accepts message Client QUIT Requests termination of Session 221 Mail Panko. Com Service Server Closing transmission channel End of transmission Server None Closes TCP connection
16 Figure 11-6: Interactions in the Simple Mail Transfer Protocol (SMTP) Actor SMTP Command Comment Server 250 OK Server accepts message. Client QUIT Requests termination of Session. Server 221 Mail.Panko.Com Service Closing transmission channel End of transmission. Client When in the course … The message. Multiple lines Of text. Ends with line Containing only a single Period: <CRLF>.<CRLF> Server None Closes TCP connection
I Figure 11-4: E-Mail Viruses, Worms, and Trojan Horses Widespread problems Often delivered by e-mail attachments Use of antivirus software is almost universal but not fully effective 17
17 Figure 11-4: E-Mail • Viruses, Worms, and Trojan Horses – Widespread Problems • Often delivered by e-mail attachments • Use of antivirus software is almost universal but not fully effective
I Figure 11-4: E-Mail New Messages With Inappropriate content Racial or sexual harassment Threats Disclosing proprietary information These must be found to prevent damage(lawsuits and loss of intellectual property) 18
18 Figure 11-4: E-Mail • Messages With Inappropriate Content – Racial or sexual harassment – Threats – Disclosing proprietary information – These must be found to prevent damage (lawsuits and loss of intellectual property) New
I Figure 11-4: E-Mail Viruses, Worms, and Trojan Horses Where to do Scanning? · On client Pcs But users often turn off their software Fail to download virus definitions regularly Or let their contracts lapse On the corporate mail server or application firewall Users cannot turn off 19
19 Figure 11-4: E-Mail • Viruses, Worms, and Trojan Horses – Where to Do Scanning? • On client PCs – But users often turn off their software, – Fail to download virus definitions regularly – Or let their contracts lapse • On the corporate mail server or application firewall – Users cannot turn off
I Figure 11-4: E-Mail Viruses, Worms, and Trojan Horses Where to do scanning? At an antivirus outsourcing company Before mail ever reaches the company High level of expertise Defense in Depth Do filtering in at least two places 20
20 Figure 11-4: E-Mail • Viruses, Worms, and Trojan Horses – Where to Do Scanning? • At an antivirus outsourcing company – Before mail ever reaches the company – High level of expertise • Defense in Depth – Do filtering in at least two places