Free Security, Specialist (JNCIS-SEC) Practice Questions

The correct answers are B and

D.  

In VPN cryptography, hashing is used for authentication and integrity checking, not confidentiality. Juniper’s IPsec documentation describes MD5 as producing a 128-bit hash, also called a digital signature or message digest, from a message of arbitrary length. It also describes SHA as producing a 160-bit hash from a message of arbitrary length. That directly supports option B because a hash function takes variable-length input and produces a fixed-size digest.

Option D is also correct because Juniper states that the resulting hash is used like a fingerprint of the input to verify content and source authenticity and integrity. Juniper’s IPsec overview further explains that Junos compares the calculated message digest against the expected digest to verify that the message has not been tampered with.

Option A is wrong because hashing is not compression; it is one-way digest generation. Option C is wrong because encryption protects confidentiality, while hashing validates integrity and authenticity. In IPsec, algorithms such as AES, DES, and 3DES provide encryption, while MD5, SHA-1, and SHA-2 provide hashing/HMAC-based authentication. Reference topics: IPsec VPN, hashing, HMAC, MD5, SHA, message digest, data integrity.

The correct answers are B and

C.  

In Junos route-based IPsec VPNs, the default proxy ID is broad: local 0.0.0.0/0, remote 0.0.0.0/0, and service any. This default behavior allows routed traffic entering the secure tunnel interface to determine what is protected by the VPN rather than requiring a narrow policy-based encryption domain. Juniper’s IPsec VPN configuration guidance also states that proxy IDs are used in Phase 2 negotiations, and that a proxy ID mismatch is one of the common causes of Phase 2 failure. For interoperability with some third-party VPN peers, Juniper notes that proxy IDs may need to be manually configured to match the peer.

Option A is wrong because proxy IDs can override default route-based behavior when manually configured, especially when a peer requires specific local and remote protected subnets. Option D is wrong because proxy IDs are not created during IKE Phase 1. Phase 1 builds the secure IKE channel; proxy IDs belong to Phase 2/IPsec SA negotiation, where the peers agree on traffic selectors for encrypted traffic. Reference topics: IPsec VPN, route-based VPNs, proxy IDs, Phase 2 negotiation, traffic selectors, third-party VPN interoperability.

The correct answers are B and

C.  

IDP false positives occur when legitimate traffic matches an attack signature or attack object incorrectly. One valid way to reduce false positives is to remove the problematic attack object from the IDP rule, especially when that object is not relevant to the protected application, server role, or traffic direction. Juniper defines attack objects as the items specified in IDP rules to identify malicious activity, so removing an irrelevant or noisy attack object directly reduces unwanted matches.

Option C is also correct because Juniper specifically recommends using an exempt rulebase when an IDP rule uses an attack object group containing attack objects that produce false positives or irrelevant log records. Exempt rules can exclude a specific source, destination, or source/destination pair from matching an IDP rule, preventing unnecessary alarms.

Option A is wrong because changing the action to a lower severity response does not reduce the false positive; it only changes what happens after the false match occurs. Option D is wrong because a terminal rule at the end of the rule base does not prevent earlier false-positive matches. Reference topics: IDP, attack objects, exempt rulebase, false-positive tuning, IDP rule matching.

The correct answers are A and

D.  

A mobile command center using a 5G ISP behind CGNAT is operating behind dynamic address translation. For IPsec to work reliably through NAT, the SRX must support NAT Traversal, which encapsulates IKE and ESP traffic in UDP/4500 after NAT is detected. Juniper states that NAT-T is used when NAT devices exist in the datapath and that NAT keepalives are required because NAT devices age out UDP translations. Juniper’s Security Director VPN workflow also specifically says to enable NAT-T when the dynamic endpoint is behind a NAT device.

DPD is also required because mobile and carrier-grade NAT connections can disappear, roam, or become stale without a clean tunnel teardown. Juniper defines Dead Peer Detection as the method used by IPsec peers to verify whether the remote peer is still present and responsive by sending encrypted IKE notification payloads and waiting for acknowledgements. Option B is not the best answer because IKEv1 aggressive mode is weaker and does not provide identity protection; Juniper also notes that aggressive mode applies only to IKEv1. Option C is invalid because IKEv2 aggressive mode does not exist. Reference topics: IPsec VPN, NAT-T, CGNAT, dynamic endpoints, DPD, IKE peer availability.

The correct answers are A and

C.  

Juniper ATP Cloud uses a malware-analysis pipeline. When a file is submitted, the first step is a cache lookup based on the file hash. Juniper explains that if the file has already been analyzed, the stored verdict is returned to the SRX Series Firewall and there is no need to re-analyze the file. That directly supports C and eliminates B, because analysis does not continue when a cached verdict is found.

If the cache lookup does not return a verdict, the remaining ATP Cloud analysis techniques are used. Juniper describes the pipeline model in which each analysis technique creates a verdict number, and those verdicts are combined into a final verdict score from 0 to 10. That final threat score is what the SRX compares against ATP Cloud policy settings to permit or block the session.

Option D is wrong because ATP Cloud does not simply return the first score generated by any one feature. The expected behavior is cumulative/final scoring across the remaining analysis pipeline. Reference topics: Juniper ATP Cloud, malware analysis pipeline, cache lookup, verdict number, threat score, SRX enforcement.