探析网络嗅探技术

网络嗅探技术在信息安全防御技术和黑客攻防技术中都处于非常重要的地位。分析了本机嗅探、广播网络嗅探和基于交换机的嗅探等网络嗅探技术的基本原理,阐述了网络嗅探技术在网络行为审计网络蠕虫病毒抑制等信息安全防御领域的作用,探讨了网络嗅探技术应用前景和发展方向。     

Prediction of enteric methane emissions from lactating cows using methane to carbon dioxide ratio in the breath

The aim of this study was to develop prediction equations for methane (CH₄) emissions from lactating cows using the CH₄/carbon dioxide (CO₂) ratio in the breath measured in the automatic milking system (AMS) and to evaluate the predicted values and factors affecting the CH₄/CO₂ ratio. The model development was conducted using a dataset determined in respiration chambers or head boxes (n = 121). Then, gas measurements in the AMS as well as in the head box were carried out with six lactating cows fed one of three different levels of neutral detergent fiber (NDF) content, following a 3 × 3 Latin square experimental design. The obtained equation that is suitable for practical use on farms to predict CH₄ was CH₄ (L/day) = −507 + 0.536 live weight (kg) + 8.76 energy-corrected milk (kg/day) + 5,029 CH₄/CO₂ (adjusted R² = 0.83; root mean square error = 40.8 L/day). Results showed that the predicted values correlated positively with the observed values, the determined CH₄/CO₂ ratio increased with increasing dietary NDF content, and the detected eructation rate was in the normal range. On the other hand, the CH₄/CO₂ ratio was affected by the time interval between measurement and last eating before the measurement.     

Network Security Monitor

Illegal traffics on network can be actively detected by network security monitor An advanced system is given which can capture network data stream and intercept malicious attack, so as to alarm or take response action in real-time. The system is composed by sniffer, monitor control center, remote management unit,etc. Attack activities under surveillance can be distinguished by two methods,which are rule based method and statistics based method. Intrusion recognition by sniffer is the key technology of the system. In addition, dilemma between real-time data stream and high inquiry speed, as well as dynamic addition of attack rules contributes to the main concern of system design. Backdoor of The system can be self detected, while intelligent analysis and bi-directional surveillance ability has also been implemented. With all these advance features, the system is presented not only as a strong assistant to traditional network security products, but also an important tool for counter-fighting with rampant network intrusion nowadays.