JN0-636 Exam Dumps : Security, Professional (JNCIP-SEC)

According to the security flow trace shown in the exhibit, which is a snippet of a packet capture on an SRX Series device, the two statements that are correct are:

• This packet arrived on interface ge-0/0/4.0. This is indicated by the line In: 10.0.1.129/22 -> 10.0.1.129/3382;1,0x0, which shows that the ingress interface of the packet is ge-0/0/4.0, as the interface name is prefixed to the source and destination IP addresses and ports of the packet1.
• An existing session is found in the table. This is indicated by the line Found: session id 0x12. sess tok 28685, which shows that the packet matches an existing session in the session table with the session ID 0x12 and the session token 286852.

The following statements are incorrect or not supported by the output:

• Destination NAT occurs. This is not supported by the output, as there is no indication of destination NAT being applied to the packet. The destination IP address of the packet is 10.0.1.129, which is the same as the destination IP address of the original packet. If destination NAT was applied, the destination IP address of the packet would be different from the destination IP address of the original packet.
• The capture is a packet from the source address 172.20.101.10 destined to 10.0.1.129. This is false, as the output shows that the source address of the packet is 10.0.1.129, not 172.20.101.10. The source IP address of the packet is prefixed to the ingress interface name ge-0/0/4.0.

References: 1: Understanding Security Flow Trace 2: show security flow session - Technical Documentation - Support - Juniper Networks

In Juniper ATP Cloud, a threat prevention policy allows you to define how the system should handle an infected host. Two of the available actions are:

• Close the connection: This action will close the connection between the infected host and the destination to which it is trying to connect. This will prevent the host from communicating with the destination and will stop any malicious activity.
• Quarantine the host: This action will isolate the infected host from the network by placing it in a quarantine VLAN. This will prevent the host from communicating with other devices on the network, which will prevent it from spreading malware or exfiltrating data.

Sending a custom message is used to notify the user and administrator of the action taken. Drop the connection silently is not an action available in Juniper ATP Cloud.

According to the Juniper documentation, the threat prevention policy in Juniper ATP Cloud is a configuration that defines the actions and notifications for different threat levels of the traffic. The threat levels are based on the verdicts returned by Juniper ATP Cloud after analyzing the files, URLs, and domains. The threat levels range from 1 to 10, where 1 is the lowest and 10 is the highest1.

The threat prevention policy allows the user to specify different actions for different threat levels. The actions can be applied to the traffic or to the infected host. The actions available for the traffic are:

• Permit: Allows the traffic to pass through the SRX Series device without any interruption.
• Block: Blocks the traffic and sends a reset packet to the client and the server.
• Drop: Drops the traffic silently without sending any reset packet.
• Redirect: Redirects the traffic to a specified URL, such as a warning page or a sinkhole server.

The actions available for the infected host are:

• None: Does not take any action on the infected host.
• Quarantine: Quarantines the infected host by applying a firewall filter that blocks all outbound traffic from the host, except for the traffic to Juniper ATP Cloud or the specified redirect URL.
• Custom: Executes a custom script on the SRX Series device to perform a user-defined action on the infected host, such as sending an email notification or triggering an external system.

Therefore, the two different actions available in a threat prevention policy to deal with an infected host are:

• Block: This action will block the traffic from or to the infected host and send a reset packet to the client and the server. This will prevent the infected host from communicating with the malicious server or spreading the malware to other hosts.
• Quarantine: This action will quarantine the infected host by blocking all outbound traffic from the host, except for the traffic to Juniper ATP Cloud or the redirect URL. This will isolate the infected host from the network and allow the user to remediate the infection.

The following actions are not available or incorrect:

• Send a custom message: This is not an action available in the threat prevention policy. However, the user can use the custom action to execute a script that can send a custom message to the infected host or the administrator.
• Drop the connection silently: This is an action available for the traffic, not for the infected host. It will drop the traffic without sending any reset packet, which may not be effective in stopping the infection or notifying the user.

References: 1: Configuring Threat Prevention Policies

Proxy ARP is a technique used by routers to answer ARP requests on one network segment on behalf of hosts on another network segment. This is useful in situations where a host on one network segment needs to communicate with a host on another network segment, but the two hosts are not directly connected. In this case, the router acts as a proxy, answering ARP requests on behalf of the other host. In the exhibit, the vSRX device is configured to use a pool of addresses that are in the same subnet as the external interface ge-0/0/0 for source NAT. This means that the vSRX device will translate the source IP address of the internal hosts to one of the addresses in the pool before sending the packets to the external network. However, the external hosts will not know how to reach the NATed addresses, since they are not directly connected to the vSRX device. They will send ARP requests for the NATed addresses, expecting to receive a MAC address from the vSRX device. If proxy ARP is not enabled on the vSRX device, it will not respond to these ARP requests, since it does not have the NATed addresses configured on its interface. The ARP requests will time out and the packets will be dropped by the external hosts or the service provider router. To solve this problem, proxy ARP must be enabled on the vSRX device for the NATed addresses. This will allow the vSRX device to respond to the ARP requests from the external hosts, providing its own MAC address as the destination. The external hosts will then send the packets to the vSRX device, which will reverse the NAT and forward the packets to the internal hosts. References:

• Configuring Proxy ARP (CLI Procedure)
• [SRX] When and how to configure Proxy ARP (https://supportportal.juniper.net/s/article/SRX-Dynamic-VPN-scenario-for-configuring-Proxy-ARP-on-SRX?language=en_US)