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Time relay, English name is me relay, is a relay that generates action only after the input action signal is added or removed, and the output circuit needs a specified accurate time. It is applied to low circuits to switch on or off high voltage and high current circuits. Time relay is also an electrical appliance that uses electromagnetic principle or principle to realize delay control, including air damping type, electric type, electronic type and other types.3. The code in the policy mode can be reused.At present, most of the articles on the Internet are transmitted through the source code and log to explain the events. For those who read the articles, the experience is not so good, and they cannot find the head in the fog. Here is a sunflower treasure book! After reading this picture, my mother no longer has to worry about my study!When an attacker sends an http get request, Slowly sending useless header fields, And never sends the "\ r\ n\ r\ n" end flag, This allows the connection to the web server to be occupied for a long time and ensures that the link is not broken by timeout. However, the number of concurrent connections that the server can handle is limited. If the attacker uses a large number of controlled hosts to send such incomplete requests and continues to occupy them, the connection resources will be exhausted (slowhttptest tool). A web server software such as iis nginx has been modified for this attack method, but web servers such as apache and dhttpd will still be attacked by slowloris.花生讨好地说道：我藏着也是留给三姐姐的。Quanzhou Scenic Spots Recommendation, Quanzhou Travel StrategySYN attack is a kind of DOS attack. It takes advantage of TCP protocol defects and consumes CPU and memory resources by sending a large number of semi-connection requests. SYN attacks can not only affect hosts, but also harm network systems such as routers and firewalls. In fact, SYN attacks can be implemented as long as these systems turn on TCP services no matter what systems are targeted. As can be seen from the above figure, the server receives the connection request (syn=j), adds this information to the unconnected queue, and sends the request packet to the client (syn=k, ack=j+1), then enters the SYN_RECV state. When the server does not receive an acknowledgement packet from the client, it retransmits the request packet and does not delete this entry from the non-connection queue until the timeout. With IP spoofing, SYN attacks can achieve good results, Typically, clients forge a large number of non-existent IP addresses in a short period of time, SYN packets are continuously sent to the server, and the server replies to the confirmation packets and waits for the confirmation of the customer. Since the source address does not exist, the server needs to continuously resend until it timeout. These forged SYN packets will occupy the unconnected queue for a long time, normal SYN requests will be discarded, the target system will run slowly, and in serious cases, the network will be blocked or even the system will be paralyzed.