DNS Security Analytics
The DNS Security service operates real-time DNS request analysis using predictive analytics and machine learning on multiple DNS data sources. This is used to generate protections for DNS-based threats, which are accessible in real-time through configuration of the Anti-Spyware Security profile attached to a Security policy rule. Each DNS threat category (the DNS Signature Source) allows allow you to define separate policy actions as well as a log severity level for a specific signature type. This enables you to create specific security policies based on the nature of the threat, according to your network security protocols. Palo Alto Networks also generates and maintains a list of explicitly allowable domains based on metrics from PAN-DB and Alexa. These allow list domains are frequently accessed and known to be free of malicious content. The DNS Security categories and the allow list are updated and extensible through PAN-OS content releases.
You can view your organization’s DNS statistics data generated by the DNS Security Cloud service using AutoFocus. This provides a fast, visual assessment describing the breakdown of DNS requests passing through your network based on the available DNS categories. Alternatively, you can retrieve domain information, as well as the transaction details, such as latency and TTL using the
test dns-proxy dns-signature fqdn <command.
Upon upgrade to PAN-OS 10.0 and later, the DNS Security source gets redefined into new categories to provide extended granular controls; as a result, the new categories will overwrite the previously defined action and acquire default settings. Make sure to reapply any sinkhole, log severity, and packet captures settings appropriate for the newly defined DNS Security Categories.
The DNS Security service currently supports detection of the following DNS threat categories:
- Command and Control Domains—C2 includes URLs and domains used by malware and/or compromised systems to surreptitiously communicate with an attacker’s remote server to receive malicious commands or exfiltrate data (this includes DNS tunneling detection and DGA detection), or deplete resources on a target authoritative DNS servers (such as NXNSattack).
- DNS Tunnel Detection—DNS tunneling can be used by attackers to encode data of non-DNS programs and protocols within DNS queries and responses. This provides attackers with an open back channel with which they can transfer files or remotely access the system. DNS tunnel detection uses machine learning to analyze the behavioral qualities of DNS queries, including n-gram frequency analysis of domains, entropy, query rate, and patterns to determine if the query is consistent with a DNS tunneling-based attack. Combined with the firewall’s automated policy actions, this allows you to quickly detect C2 or data theft hidden in DNS tunnels and to automatically block it, based on your defined policy rules.
- DGA Detection—Domain generation algorithms (DGAs) are used to auto-generate domains, typically in large numbers within the context of establishing a malicious command-and-control (C2) communications channel. DGA-based malware (such as Pushdo, BankPatch, and CryptoLocker) limit the number of domains from being blocked by hiding the location of their active C2 servers within a large number of possible suspects, and can be algorithmically generated based on factors such as time of day, cryptographic keys, dictionary-derived naming schemes, and other unique values. While most domains generated by a DGA do not resolve as a valid domain, they must all be identified to fully defend against a given threat. DGA analysis determines whether a domain is likely to have been generated by a machine, rather than a person, by reverse-engineering and analyzing other frequently used techniques found in DGAs. Palo Alto Networks then uses these characteristics to identify and block previously unknown DGA-based threats in real-time.
- NXNSAttack—The NXNSAttack vulnerability present in the DNS protocol affects all recursive DNS resolvers and can be used by malicious actors to launch DDos-like amplification attacks to disrupt the normal operation of vulnerable authoritative DNS servers. NXNSAttack can introduce massive traffic spikes on an authoritative DNS server by forcing the recursive DNS resolver to issue a large number of invalid requests to potentially shut down the server.
- DNS Rebinding—DNS rebinding attacks lure users to an attacker-controlled domain configured with a short TTL parameter to manipulate how domain names are resolved to exploit and bypass the same-origin policy in browsers. This enables malicious actors to use the client machine as an intermediary to attack or access a resource contained within a private network.
- Dynamic DNS Hosted Domains—Dynamic DNS (DDNS) services provide mapping between hostnames and IP addresses in near real-time to keep changing IP addresses linked to a specific domain, when static IPs are unavailable. This provides attackers a method of infiltrating networks by using DDNS services to change the IP addresses that host command-and-control servers. Malware campaigns and exploit kits can utilize DDNS services as part of their payload distribution strategy. By utilizing DDNS domains as part of their hostname infrastructure, adversaries can change the IP address associated with given DNS records and more easily avoid detection. DNS Security detects exploitative DDNS services by filtering and cross-referencing DNS data from various sources to generate candidate lists which are then further validated to maximize accuracy.
- Malware Domains—Malicious domains host and distribute malware and can include websites that attempt to install various threats (such as executables, scripts, viruses, drive-by downloads). Malicious domains are distinguishable from C2 domains in that they deliver malicious payloads into your network via an external source, whereas with C2, infected endpoints typically attempt to connect to a remote server to retrieve additional instructions or other malicious content.
- Newly Registered Domains—Newly registered domains are new, never registered domains, that have been recently added by a TLD operator or entity. While new domains can be created for legitimate purposes, the vast majority are often used to facilitate malicious activities, such as operating as C2 servers or used to distribute malware, spam, PUP/adware. Palo Alto Networks detects newly registered domains by monitoring specific feeds (domain registries and registrars) and using zone files, passive DNS, WHOIS data to detect registration campaigns.
- Phishing Domains—Phishing domains attempt to lure users into submitting sensitive data, such as personal information or user credentials, by masquerading as legitimate websites through phishing or pharming. These malicious activities can be conducted through social engineering campaigns (whereby a seemingly trusted source manipulates users into submitting personal information via email or other forms of electronic communications) or through web traffic redirection, which directs users to fraudulent sites that appear legitimate.
- Grayware Domains—(Available with installation of PAN-OS content release 8290 and later). Grayware domains generally do not pose a direct security threat, however, they can facilitate vectors of attack, produce various undesirable behaviors, or might simply contain questionable/offensive content.These can include websites that:
- Attempt to trick users into granting remote access.
- Contain adware and other unsolicited applications (such as cryptominers, hijackers, and PUPs [potentially unwanted programs]).
- Deploy domain identification concealment actions using fast flux techniques.
- Demonstrate malicious behavior and usage as evidenced through DNS security predicative analytics (malicious NRD).
- Take advantage of user errors when entering web page addresses (typosquatting domains).
- Redirect traffic from a legitimate source to a malicious website due to an improperly configured or stale DNS record on an authoritative DNS server that has not been removed or otherwise corrected (dangling DNS).
- Promote illegal activities or scams.
- Parked Domains—(Available with installation of PAN-OS content release 8318 and later) Parked domains are typically inactive websites that host limited content, often in the form of click-through ads which may generate revenue for the host entity, but generally do not contain content that is useful to the end user. While they often function as a legitimate placeholder or as nothing more than a benign nuisance, they could also be used as a possible vector for distribution of malware.
- Proxy Avoidance and Anonymizers—(Available with installation of PAN-OS content release 8340 and later) Proxy Avoidance and Anonymizers is traffic to services that are used to bypass content filtering policies. Users who attempt to circumvent an organization’s content filtering policies via anonymizer proxy services are blocked at the DNS level.
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