ccna 200-301 example questions

ccna 200-301 example questions.1.2 Viruses, Worms, and Trojans 13One-third of the software vulnerabilities identified by CERT are reported to be related to buffer overflows. A buffer is an allocated area of memory that a process uses to temporarily store data. A buffer overflow occurs when a fixed length buffer reaches its capacity value and if a process attempts to store data beyond this maximum limit. This can result in the excess data overwriting adjacent memory locations as well as causing other unintended behavior. Buffer overflows are often the primary avenue for viruses, worms, and Trojan horses to do damage.Viruses and Trojans tend to exploit local root buffer overflows. A root buffer overflow is a type of buffer overflow intended to gain root access to the system. A local root buffer overflow requires certain types of actions from the end user or the system. Typical events that trigger a root buffer overflow include a user opening an email attachment, visiting a site, or exchanging files via instant messaging.Worms such as SQLSlammer and Code Red exploit remote root buffer overflows. A remote root buffer overflow is similar to a local root buffer overflow, but does not require local end-user or system intervention.1.2.4.2 Anti-virus SoftwareViruses, worms, and Trojan horses are capable of causing serious problems on networks and end systems. Network administrators have a variety of means to mitigate these attacks.Note: Mitigation techniques are often referred to as countermeasures in the security field.The primary means of mitigating virus and Trojan horse attacks is anti-virus software. Anti-virus software helps prevent hosts from being infected and spreading malicious code. Anti-virus software takes far more time to clean up infected computers than it does to keep these machines up to date with anti-virus software and virus libraries.Anti-virus software is the most widely deployed security product on the market today. Several companies that produce antivirus software, such as Symantec, Computer Associates, McAfee, and TrendMicro, have been in the business of detecting and eliminating viruses for more than a decade. Many companies and educational institutions purchase bulk licenses for their users. Users are able to use their accounts to log in to the website and download the anti-virus software to their desktops, laptops or servers.The anti-virus software has an automatic update option so that new virus databases and new software updates can be downloaded automatically or as needed. This task is the most critical requirement for keeping a network virus free and should be formally written into a network security policy.