JN0-232 Security, Associate (JNCIA-SEC) Questions and Answers

Content filtering on SRX devices inspects and controls specific file types transferred across certain application protocols:

SMTP (Option A):Supported. Content filtering can block specific file attachments in emails.

HTTP (Option D):Supported. Content filtering can block downloads of specific file types over web traffic.

SNMP (Option B):Not supported; SNMP is a management protocol, not a content delivery protocol.

TFTP (Option C):Not supported by content filtering.

Correct Protocols:SMTP and HTTP

PAT (Port Address Translation), also called NAT overload, allows many devices to share a single public IP:

Option C:Correct. Multiple internal hosts share a single external IP.

Option D:Correct. Each internal host is mapped to the same public IP but differentiated by unique port numbers.

Option A:This describes basic static NAT (1-to-1 mapping).

Option B:Incorrect, this describes general NAT behavior but not specific to PAT.

Correct Statements:PAT enables multiple internal devices to share one external IP, and it maps internal IPs to external IP + port.

The antivirus feature on SRX relies on signature definition files that must be regularly updated. To check the status of these updates, the correct operational command is:

show security utm anti-virus status(Option D). This displays details such as:

Antivirus engine status

Last update time of virus definitions

Version of the signature database

Other options:

Content-filtering statistics (Option A) shows counters for file-type filtering, not antivirus updates.

Anti-spam status (Option B) shows spam filtering engine connectivity.

Web filtering status (Option C) shows SBL/web filter server connection details.

Correct Command:show security utm anti-virus status

TheSBL (SurfControl Web Filtering)server integration is part of UTM web filtering on SRX. To confirm that the firewall is properly connected and communicating with the SBL server, the command used is:

show security web filtering status

This command displays connectivity information with the SBL server, license status, and filtering operations.

Other options:

Anti-virus (Option A) checks antivirus engine status.

Content-filtering statistics (Option C) shows local content filtering counters.

Anti-spam status (Option D) checks spam engine connectivity.

Correct Command:show security web filtering status

Unified security policies (USPs) provide integrated application-aware controls usingAppIDand extend traditional zone-based policy enforcement.

Option A:Correct. If traffic matches a unified security policy, it is not re-evaluated by traditional security policies. Unified policies take precedence for matched flows.

Option B:Incorrect. Traditional policies rely on Layer 3/4 attributes. Unified policies go deeper by leveraging AppID, which inspects traffic up to Layer 7.

Option C:Incorrect. Traffic matching a traditional policy is unaffected by unified policy unless unified mode is explicitly configured for those flows.

Option D:Correct. Dynamic application recognition in unified policies usesLayer 7 (application-layer) inspectionvia AppID.

Correct Statements:A and D

When a packet enters an SRX interface, aroute lookupis performed:

It determines theegress interface(Option B) by checking the destination IP against the routing table.

Once the egress interface is known, its associatedegress security zone(Option D) is also determined.

Theingress interface (Option A)is already known when the packet arrives, so the route lookup does not determine it.

DNS name (Option C):DNS is unrelated to routing lookups.

Correct Results:egress interface, egress security zone

Security policies on SRX support several actions:

Permit:Allows traffic to pass according to the rule.

Deny:Silently drops the traffic without notifying the source.

Reject:Drops the trafficand sends a TCP RST (for TCP) or ICMP unreachable (for UDP/other protocols)back to the source. This provides feedback to the sending host.

Next-policy:Allows policy chaining to evaluate the next policy set.

Therefore, the action that causes traffic to drop and a message to be sent to the source isreject.

Default assignment:All logical interfaces are placed in thenull zone by defaultuntil explicitly assigned to a user-defined security zone (Option A is correct).

Removal from null zone:Once an interface is assigned to a security zone, it is removed from the null zone (Option D is correct).

No traffic acceptance:The null zone is a discard zone; it cannot be configured to accept any traffic (Option C is incorrect).

Policy behavior:Traffic rejected by a security policy is dropped according to the policy action. It is not forwarded to the null zone for logging (Option B is incorrect).

Correct Statements:A and D

Juniper SRX evaluatessecurity policies in order, top to bottom. The first matching policy determines the action, and no further policies are evaluated. This behavior can lead toshadowed policiesif later policies match the same conditions as earlier ones.

From the exhibit:

Policy1:Matches application junos-http and permits traffic.

Policy2:Matches application junos-https and permits traffic.

Policy3:Matches application junos-http again, but denies traffic.

Sincepolicy1already matches all HTTP traffic and permits it, traffic never reachespolicy3. This makespolicy3 shadowedbecause it has the same match condition as policy1 but is evaluated later in the list.

Other options:

Policy1 is not shadowed because it is evaluated first.

Policy2 is independent (application = HTTPS) and therefore unaffected.

Only policy3 is shadowed by policy1.

Correct Statement:Policy3 will be shadowed because it matches the same application as policy1.

NAT processing in Junos OS follows a strict sequence to ensure correct packet handling:

Static NAT– applied first because it provides a permanent one-to-one bidirectional mapping.

Destination NAT– applied second to translate inbound destination addresses, often used for servers in private networks.

Source NAT– applied last to translate outbound private source addresses to public ones.

This ensures deterministic behavior and avoids conflicts between translation types.

Options B, C, and D list incorrect sequences.

Correct Order:static NAT → destination NAT → source NAT

NAT rule processing on SRX devices follows a deterministic order:

Top-to-bottom order (Option C):NAT rules are always evaluated in the order they appear in the configuration, starting at the top.

First-match wins (Option B):Once a packet matches a NAT rule, processing stops.

Option A:Incorrect. Not all rules are processed; evaluation stops at the first match.

Option D:Incorrect. NAT rules are never processed bottom-to-top.

Correct Statements:NAT rule processing stops at the first match, and NAT rules are processed top-to-bottom.

Intra-zone traffic:On SRX devices, traffic between interfaces in the same security zone is allowedwithout requiring a security policy(Option C is correct). Policies are only evaluated for inter-zone traffic.

Junos-host functional zone:This zone is a predefined functional zone that allows administrators to apply policies controlling access to the SRX firewall itself, such as SSH, HTTP, or SNMP traffic (Option D is correct).

Null zone:This zone is a predefined discard zone. Interfaces placed in the null zone drop all traffic. It does not allow policy logging of dropped control plane traffic (Option A is incorrect).

Management functional zone:This is used to define management interfaces, not the “functional zone” as stated in Option B (incorrect wording).

Correct Statements:C and D

Inbound Flow (before NAT):Source =10.20.30.40(internal private IP)Destination =203.0.113.1(public DNS server)

Outbound Flow (after NAT):Source =192.0.2.1(translated IP)Destination =203.0.113.1(unchanged)

Analysis:

Thesource IP (10.20.30.40)was translated to192.0.2.1. This indicatesSource NATwas applied →Option B is correct.

Thedestination IP changedbetween the inbound and outbound view. Inbound it was203.0.113.1, and outbound it is still203.0.113.1in appearance, but notice the reversal: the session entry shows it as the outbound "source" side. This confirmsDestination NAT translation has occurredfor return flow consistency →Option D is correct.

Option A:Incorrect. The original source IP was indeed translated.

Option C:Incorrect. The destination IP did change in the flow processing.

Correct Statements:

The original source IP address was translated to a new source IP address.

The original destination IP address was translated to a new destination IP address.

To enforce acatch-all blocking policyafter other specific policies, the correct solution is aglobal security policy (Option A).

Global policiescan apply universally across zones, and an administrator can configure a final “deny all” rule to block any unmatched traffic.

ATP policy (Option B):Protects against advanced threats, not used for catch-all rule enforcement.

IDP policy (Option C):Focuses on intrusion detection and prevention signatures, not general traffic blocking.

Integrated user firewall policy (Option D):Applies policies based on user identity, but it does not provide a universal block across all services.

Correct Solution:Global security policy

SRX Series devices providecontent securityfeatures that rely on advanced identification mechanisms. File identification is not based merely on file extensions (which can be easily spoofed), but instead ondeep inspection techniques:

AppID (Application Identification):AppID is part of the AppSecure suite, allowing the device to classify applications and content regardless of port or protocol. This enables the SRX to detect applications and their related content for enforcement.

Protocol-based file type identification:The SRX can recognize and identify file types embedded withinHTTP, FTP, and e-mail (SMTP, IMAP, POP3) protocols. This providesaccurate content inspection and filtering, independent of file naming conventions.

Why not the others?

File extensions (Option A) are not reliable for content security, so SRX does not use them.

ALGs (Option D) are used for protocol handling, such as SIP or FTP control channels, not for content identification.

The packet processing order in SRX with NAT and policies is:

Destination NAT(applies first, for inbound traffic).

Security Policy Evaluation(after destination NAT, before source NAT).

Source NAT(applies last, for outbound traffic).

Option A:Incorrect. Policies are not evaluated before destination NAT.

Option B:Correct. Security policies are evaluatedbefore source NATbut after destination NAT. So in terms of order, policies are processed prior to source NAT.

Option C:Incorrect. Policies are not evaluated before source NAT — they are evaluatedbefore source NAT is applied.

Option D:Correct. Policies are evaluatedafter destination NAT.

Correct Statements:B and D