Threat Signature Categories

There are three types of Palo Alto Networks threat signatures, each designed to detect different types of threats as the firewall scans network traffic:
  • Antivirus signatures—Detect viruses and malware found in executables and file types.
  • Anti-spyware signatures—Detects command-and-control (C2) activity, where spyware on an infected client is collecting data without the user's consent and/or communicating with a remote attacker.
  • Vulnerability signatures—Detects system flaws that an attacker might otherwise attempt to exploit.
A signature's severity indicates the risk of the detected event, and a signature's default action (for example, block or alert) is how Palo Alto Networks recommends that you enforce matching traffic.
You must Set Up Antivirus, Anti-Spyware, and Vulnerability Protection to tell the firewall what action to take when it detects a threat, and you can easily use the default security profiles to start blocking threats based on Palo Alto Networks recommendations. For each signature type, category, and even specific signatures you can continue to modify or create new profiles to more granularly enforce potential threats.
The following table lists all possible signature categories by type—Antivirus, Spyware, and Vulnerability—and includes the content update (Applications and Threats, Antivirus, or WildFire) that provides the signatures in each category. You can also go to the Palo Alto Networks Threat Vault to Learn More About Threat Signatures.
Threat Category
Content Update that Provides These Signatures
Description
Antivirus Signatures
apk
Antivirus
WildFire or WildFire Private
Malicious Android Application (APK) files.
dmg
Antivirus
WildFire or WildFire Private
Malicious Apple disk image (DMG) files, that are used with Mac OS X.
flash
Antivirus
Wildfire or WildFire Private
Adobe Flash applets and Flash content embedded in web pages.
java-class
Antivirus
Java applets (JAR/class file types).
macho
Antivirus
Wildfire or WildFire Private
Mach object files (Mach-O) are executables, libraries, and object code that are native to Mac OS X.
office
Antivirus
Wildfire or WildFire Private
Microsoft Office files, including documents (DOC, DOCX, RTF), workbooks (XLS, XLSX), and PowerPoint presentations (PPT, PPTX).
openoffice
Antivirus
Wildfire or WildFire Private
Office Open XML (OOXML) 2007+ documents.
pdf
Antivirus
Wildfire or WildFire Private
Portable Document Format (PDF) files.
pe
Antivirus
Wildfire or WildFire Private
Portable executable (PE) files can automatically execute on a Microsoft Windows system and should be only allowed when authorized. These files types include:
  • Object code.
  • Fonts (FONs).
  • System files (SYS).
  • Driver files (DRV).
  • Windows control panel items (CPLs).
  • DLLs (dynamic-link libraries).
  • OCXs (libraries for OLE custom controls, or ActiveX controls).
  • SCRs (scripts that can be used to execute other files).
  • Extensible Firmware Interface (EFI) files, which run between an OS and firmware in order to facilitate device updates and boot operations.
  • Program information files (PIFs).
pkg
Antivirus
Wildfire or WildFire Private
Apple software installer packages (PKGs), used with Mac OS X.
Spyware Signatures
adware
Applications and Threats
Detects programs that display potentially unwanted advertisements. Some adware modifies browsers to highlight and hyperlink the most frequently searched keywords on web pages-these links redirect users to advertising websites. Adware can also retrieve updates from a command-and-control (C2) server and install those updates in a browser or onto a client system.
Newly-released protections in this category are rare.
autogen
Antivirus
These payload-based signatures detect command-and-control (C2) traffic and are automatically-generated. Importantly, autogen signatures can detect C2 traffic even when the C2 host is unknown or changes rapidly.
backdoor
Applications and Threats
Detects a program that allows an attacker to gain unauthorized remote access to a system.
botnet
Applications and Threats
Indicates botnet activity. A botnet is a network of malware-infected computers (“bots”) that an attacker controls. The attacker can centrally command every computer in a botnet to simultaneously carry out a coordinated action (like launching a DoS attack, for example).
browser-hijack
Applications and Threats
Detects a plugin or software that is modifying browser settings. A browser hijacker might take over auto search or track users’ web activity and send this information to a C2 server.
Newly-released protections in this category are rare.
cryptominer
Applications and Threats
(Sometimes known as cryptojacking or miners) Detects the download attempt or network traffic generated from malicious programs designed to use computing resources to mine cryptocurrencies without the user's knowledge. Cryptominer binaries are frequently delivered by a shell script downloader that attempts to determine system architecture and kill other miner processes on the system. Some miners execute within other processes, such as a web browser rendering a malicious web page.
data-theft
Applications and Threats
Detects a system sending information to a known C2 server.
Newly-released protections in this category are rare.
dns
Antivirus
Detects DNS requests to connect to malicious domains.
dns and dns-wildfire signatures detect the same malicious domains; however, dns signatures are included in the daily Antivirus content update and dns-wildfire signatures are included in the WildFire updates that release protections every 5 minutes.
dns-security
Antivirus
Detects DNS requests to connect to malicious domains.
dns-security includes signatures from dns and dns-wildfire in addition to the unique signatures generated by the DNS Security service.
dns-wildfire
Wildfire or WildFire Private
Detects DNS requests to connect to malicious domains.
dns and dns-wildfire signatures detect the same malicious domains; however, dns signatures are included in the daily Antivirus content update and dns-wildfire signatures are included in the WildFire updates that release protections every 5 minutes.
downloader
Applications and Threats
(Also known as droppers, stagers, or loaders) Detects programs that use an internet connection to connect to a remote server to download and execute malware on the compromised system. The most common use case is for a downloader to be deployed as the culmination of
stage one
of a cyber attack, where the downloader’s fetched payload execution is considered
second stage
. Shell scripts (Bash, PowerShell, etc.), trojans, and malicious lure documents (also known as maldocs) such as PDFs and Word files are common downloader types.
fraud
Applications and Threats
(Including form-jacking, phishing, and scams) Detects access to compromised websites that have been determined to be injected with malicious JavaScript code to collect sensitive user information. (for example, Name, address, email, credit card number, CVV, expiration date) from payment forms that are captured on the checkout pages of e-commerce websites.
hacktool
Applications and Threats
Detects traffic generated by software tools that are used by malicious actors to conduct reconnaissance, attack or gain access to vulnerable systems, exfiltrate data, or create a command and control channel to surreptitiously control a computer system without authorization. These programs are strongly associated with malware and cyber attacks. Hacking tools might be deployed in a benign manner when used in Red and Blue Team operations, penetration tests, and R&D. The use or possession of these tools may be illegal in some countries, regardless of intent.
keylogger
Applications and Threats
Detects programs that allow attackers to secretly track user activity, by logging keystrokes and capturing screenshots.
Keyloggers use various C2 methods to periodically sends logs and reports to a predefined e-mail address or a C2 server. Through keylogger surveillance, an attacker could retrieve credentials that would enable network access.
networm
Applications and Threats
Detects a program that self-replicates and spreads from system to system. Net-worms might use shared resources or leverage security failures to access target systems.
phishing-kit
Applications and Threats
Detects when a user attempts to connect to a phishing kit landing page (likely after receiving an email with a link to the malicious site). A phishing website tricks users into submitting credentials that an attacker can steal to gain access to the network.
In addition to blocking access to phishing kit landing pages, enable Multi-Factor Authentication and Credential Phishing Prevention to prevent phishing attacks at all stages.
post-exploitation
Applications and Threats
Detects activity that indicates the post-exploitation phase of an attack, where an attacker attempts to assess the value of a compromised system. This might include evaluating the sensitivity of the data stored on the system, and the system’s usefulness in further compromising the network.
webshell
Applications and Threats
Detects web shells and web shell traffic, including implant detection and command and control interaction. Web shells must first be implanted by a malicious actor onto the compromised host, most often targeting a web server or framework. Subsequent communication with the web shell file frequently enables a malicious actor to establish a foothold in the system, conduct service and network enumeration, data exfiltration, and remote code execution in the context of the web server user. The most common web shell types are PHP, .NET, and Perl markup scripts. Attackers can also use web shell-infected web servers (the web servers can be both internet-facing or internal systems) to target other internal systems.
spyware
Applications and Threats
Detect outbound C2 communication. These signatures are either auto-generated or are manually created by Palo Alto Networks researchers.
Spyware and autogen signatures both detect outbound C2 communication; however, autogen signatures are payload-based and can uniquely detect C2 communications with C2 hosts that are unknown or change rapidly.
Vulnerability Signatures
brute force
Applications and Threats
A brute-force signature detects multiple occurrences of a condition in a particular time frame. While the activity in isolation might be benign, the brute-force signature indicates that the frequency and rate at which the activity occurred is suspect. For example, a single FTP login failure does not indicate malicious activity. However, many failed FTP logins in a short period likely indicate an attacker attempting password combinations to access an FTP server.
You can tune the action and trigger conditions for brute force signatures.
code execution
Applications and Threats
Detects a code execution vulnerability that an attacker can leverage to run code on a system with the privileges of the logged-in user.
code-obfuscation
Applications and Threats
Detects code that has been transformed to conceal certain data while retaining its function. Obfuscated code is difficult or impossible to read, so it’s not apparent what commands the code is executing or with which programs its designed to interact. Most commonly, malicious actors obfuscate code to conceal malware. More rarely, legitimate developers might obfuscate code to protect privacy, intellectual property, or to improve user experience. For example, certain types of obfuscation (like minification) reduce file size, which decreases website load times and bandwidth usage.
dos
Applications and Threats
Detects a denial-of-service (DoS) attack, where an attacker attempts to render a targeted system unavailable, temporarily disrupting the system and dependent applications and services. To perform a DoS attack, an attacker might flood a targeted system with traffic or send information that causes it to fail. DoS attacks deprive legitimate users (like employees, members, and account holders) of the service or resource to which they expect access.
exploit-kit
Applications and Threats
Detects an exploit kit landing page. Exploit kit landing pages often contain several exploits that target one or many common vulnerabilities and exposures (CVEs), for multiple browsers and plugins. Because the targeted CVEs change quickly, exploit-kit signatures trigger based on the exploit kit landing page, and not the CVEs.
When a user visits a website with an exploit kit, the exploit kit scans for the targeted CVEs and attempts to silently deliver a malicious payload to the victim’s computer.
info-leak
Applications and Threats
Detects a software vulnerability that an attacker could exploit to steal sensitive or proprietary information. Often, an info-leak might exist because comprehensive checks do not exist to guard the data, and attackers can exploit info-leaks by sending crafted requests.
insecure-credentials
Applications and Threats
Detects the use of weak, compromised, and manufacturer default passwords for software, network appliances, and IoT devices.
overflow
Applications and Threats
Detects an overflow vulnerability, where a lack of proper checks on requests could be exploited by an attacker. A successful attack could lead to remote code execution with the privileges of the application, server or operating system.
phishing
Applications and Threats
Detects when a user attempts to connect to a phishing kit landing page (likely after receiving an email with a link to the malicious site). A phishing website tricks users into submitting credentials that an attacker can steal to gain access to the network.
In addition to blocking access to phishing kit landing pages, enable Multi-Factor Authentication and Credential Phishing Prevention to prevent phishing attacks at all stages.
protocol-anomaly
Applications and Threats
Detects protocol anomalies, where a protocol behavior deviates from standard and compliant usage. For example, a malformed packet, poorly-written application, or an application running on a non-standard port would all be considered protocol anomalies, and could be used as evasion tools. It is a best practice to block protocol anomalies of any severity.
sql-injection
Applications and Threats
Detects a common hacking technique where an attacker inserts SQL queries into an application’s requests, in order to read from or modify a database. This type of technique is often used on websites that do not comprehensively sanitize user input.

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