What is Packet Sniffing?

What is network sniffing software used for?

Network sniffing software monitors data traveling across a network. Cybersecurity professionals and IT teams use these tools to troubleshoot connectivity issues, detect suspicious traffic, and analyze network performance. However, cybercriminals can also abuse packet sniffing tools to intercept unencrypted data such as login credentials, messages, and browsing activity.

Packet sniffers were originally developed for legitimate network monitoring and troubleshooting purposes. While they can still be used in this way, it is common for this helpful tool to be manipulated for malicious purposes. Take a look below at the good and the bad uses for sniffers:

The good

• Network engineers can use sniffers to analyze the traffic on their network and restructure their platform for optimum speed and efficiency. For example, network engineers often use packet analyzers like Wireshark to troubleshoot slow VoIP calls, identify packet loss, investigate DNS failures, or pinpoint devices generating abnormal traffic inside a corporate network.
• Employers may deploy sniffers to monitor their employees at work. This is an easy way for them to determine whether employees are spending sufficient time on their work or if they are too busy googling cats. In legitimate workplace environments, organizations may monitor network traffic to enforce security policies, prevent data leaks, detect unauthorized software usage, or investigate suspicious activity on company-managed devices.
• Security support teams can detect unusual amounts of traffic or irregular types of traffic which can identify possible threats. Hackers will often be detected by security teams by the irregularity of traffic when the hacker is present. Security teams also use network monitoring tools to identify indicators of compromise such as unusual outbound traffic, repeated failed login attempts, suspicious DNS requests, or unexpected communication with known malicious servers.
• System administrators can use sniffers as troubleshooters. By identifying where the traffic is most slowed down, it can help them highlight issues that need solving in the chain.
• White Hat Hackers can be hired by companies to hack their own networks in order to test their network security systems currently in place and discover potential gaps or flaws in their security systems.

The bad

• Cybercriminals will exploit online sniffers to gain access to private and confidential information. Since sniffers can detect all the traffic going to and from your device, hackers can gain access to any important credentials shared over email and instant messages.

Criminals will try to get you to download their malicious sniffers by sending potential targets to infected websites, or by using phishing scams to penetrate your device. Once criminals have gained access to your personal data it can lead to you being doxxed or held at ransom.

Packet sniffing attacks are most dangerous on unsecured or poorly encrypted networks. Modern HTTPS websites and end-to-end encrypted messaging apps significantly reduce the amount of readable data attackers can intercept, although cybercriminals may still attempt phishing attacks, session hijacking, or fake Wi-Fi hotspot scams to steal sensitive information.

Common types of packet sniffers

There are several types of packet sniffers used for network monitoring and traffic analysis. Some are designed for legitimate cybersecurity and troubleshooting purposes, while others may be abused for surveillance or unauthorized interception of sensitive information.

• Hardware packet sniffers are physical monitoring devices commonly used in enterprise environments, data centers, and security operations centers to analyze large volumes of network traffic.
• Software packet sniffers run directly on computers or mobile devices. Popular examples include Wireshark and tcpdump, which cybersecurity professionals often use to troubleshoot network problems, inspect packets, and investigate suspicious activity.
• Wireless packet sniffers focus on monitoring Wi-Fi traffic. Attackers may abuse these tools on unsecured wireless networks or fake public hotspots to intercept nearby traffic from connected devices.

What information can packet sniffers capture?

Depending on the type of network and whether traffic is encrypted, packet sniffers may capture sensitive information traveling between devices. This can include login credentials, browsing activity, session cookies, DNS requests, email contents, IP addresses, and unencrypted chat messages.

Modern HTTPS websites and encrypted messaging apps help reduce the amount of readable information attackers can intercept. However, cybercriminals may still collect metadata such as device information, connection details, or visited domains on unsecured networks.

How does packet sniffing work

Packet sniffing works by capturing and analyzing small units of network traffic called data packets as they move between devices. Network analyzers can inspect this traffic to troubleshoot performance issues or detect suspicious activity. In malicious scenarios, attackers may attempt to intercept unencrypted packets to collect sensitive information such as passwords or session data.

There are two main sniffing techniques commonly used. Which one is used all depends of the type of network attempting to be sniffed.

Passive sniffing

Passive sniffing is the simplest form of sniffing. It is deployed on network hubs which connect multiple different devices together under one network. As the hub ensures all devices receive all types of traffic, sniffers do not need to be advanced to be deployed into this network as they will receive all the data being shared between receivers.

Active sniffing

The more devices connected to a hub can slow down the performance due to the increased levels of traffic. Network switches can be installed to ensure that each device is only receiving the intended data. Active sniffing will need to breach these switches by sending increased levels of traffic into the network. While this is a more aggressive process it makes it much easier to identify the presence of a sniffer due to the spike in traffic levels that can be easily detected.

How to detect a packet sniffer

Detecting a packet sniffer can be difficult because many monitoring tools are designed to operate silently in the background. However, unusual network behavior, unexpected system activity, unauthorized apps, or suspicious device permissions can sometimes indicate that monitoring software or spyware is present.

• Sudden loss of storage space: While sniffers rely on stealth, they often have to store their data they are collecting somewhere - this makes them easier to identify, as if you see your storage space has depleted much more significantly than it should have, you might have found yourself a sniffer. On iPhone and Android devices, unexplained storage usage may also come from hidden spyware apps storing screenshots, recordings, or collected activity logs in the background. Reviewing recently installed apps and checking app permissions can help identify suspicious behavior.
• Unexplainable processes: Sniffers will often leach onto your user account on your PC to begin operating. A good thing to help you identify a sniffer is if you can see unexpected processors operating on your account. On Windows PCs, users can review suspicious background activity through Task Manager or Resource Monitor. Mac users can use Activity Monitor to check for unfamiliar processes consuming network resources. On mobile devices, unusual battery drain, overheating, or unexpected permission requests may also indicate spyware activity.

How to detect a packet sniffer

In some cases, network-related warning signs may indicate that traffic is being intercepted or monitored. Users may notice unusual browser redirects, repeated login prompts, suspicious SSL certificate warnings, unknown devices connected to Wi-Fi, or unexpected spikes in network activity.

On mobile devices, spyware-related activity may also include overheating, excessive battery drain, unexplained data usage, or apps requesting unnecessary access to permissions such as location services, microphone access, contacts, or photos.

Packet sniffing vs man-in-the-middle attacks

Packet sniffing and man-in-the-middle (MITM) attacks are closely related but not identical. Packet sniffing usually focuses on monitoring or capturing network traffic, while MITM attacks actively intercept and sometimes alter communications between two parties without their knowledge.

Cybercriminals may combine packet sniffing with techniques such as fake Wi-Fi hotspots, Address Resolution Protocol (ARP) spoofing, or session hijacking to steal sensitive information from connected users.

Packet sniffing:

• Primarily monitors or captures traffic
• May be passive and difficult to detect
• Often targets unencrypted communications

Man-in-the-middle attacks:

• Intercept and potentially modify communications
• Commonly involve fake networks or spoofing techniques
• May redirect users to malicious websites or login pages

How to prevent network sniffing

Preventing network sniffing usually requires a combination of encrypted connections, secure browsing habits, updated devices, and proactive monitoring for suspicious activity. While no single tool can eliminate every risk, layered security practices significantly reduce the chances of attackers intercepting sensitive information.

Below are some of the most helpful tips and tricks to keep you safe from potential harmful sniffers:

• Install security software. The easiest way to defend against online hackers is by reinforcing your security. Finding a reputable provider who can back you up against the dangers of the internet can be the most reliable way to try and fend off the pesky scammers.
• Encrypt your data using a VPN. Encrypting your data is the wisest solution to ensure any attacks that do breach your security systems will be in vain. Data with an encryption is useless to online scammers which makes it a handy way to protect your private information.
• Don’t visit unencrypted domains. Keep an eye out for the padlock in the URL of websites you are visiting online. This symbol shows that the domain is protected and you won’t need to worry about information being leaked when using the website — alternatively the HTTPS URLs also indicate that the website has been verified and secured from data leaks.
• Don’t use public Wi-Fi. As tempting as it can be to connect to the shopping malls free public access Wi-Fi network, this can often be a hotbed for potential sniffer attacks seeing as the amount of potential targets that may access this network on a daily basis. The best way to keep your data safe is staying off Wi-Fi networks which don’t require a password.
• Stay away from unencrypted messaging apps. Stick to the well known messenger apps on your phone such as Telegram, WhatsApp, and Viber to make sure the information your are sending to your friends and family is 100% secure.

If you’re concerned about spyware or hidden monitoring tools collecting data from your phone, Clario Anti Spy’s Hidden app scan can help identify suspicious apps that may be operating without your knowledge. The feature scans your iPhone or Android device for spyware-like behavior, hidden monitoring apps, and unusual permission requests that could expose sensitive information such as your location, messages, contacts, photos, or microphone access.

Here’s how to use Hidden app scan in Clario Anti Spy:

1. Open Clario Anti Spy on your iPhone or Android device and activate your subscription.
2. Tap Scan under the Hidden app scan feature.
3. Wait while the app checks your device for suspicious apps and risky permissions.
4. Review the scan results carefully.
5. If Clario Anti Spy flags an app as suspicious, follow the on-screen recommendations to remove the app and improve your device privacy.

Is packet sniffing illegal?

Packet sniffing itself is not always illegal because cybersecurity professionals and IT administrators often use packet analyzers for legitimate troubleshooting, security testing, and network monitoring purposes. However, intercepting network traffic without authorization may violate privacy laws, workplace policies, or cybersecurity regulations depending on the country or situation.

Ethical hackers and security teams typically perform packet analysis only within authorized environments where users or organizations have granted permission.

Conclusion

Packet sniffing tools can help cybersecurity professionals monitor network activity and troubleshoot security issues, but in the wrong hands, they can also expose sensitive information through spyware, malicious monitoring apps, and unsecured connections. Protecting yourself starts with safer online habits, encrypted services, updated devices, and regular checks for suspicious activity on your phone or network.

If you’re concerned about hidden monitoring tools or unauthorized access to your personal data, Clario Anti Spy can help you identify potential privacy risks on your iPhone or Android device. Features like Hidden app scan help detect suspicious apps and risky permissions that may expose sensitive information without your knowledge, helping you take action before your privacy is compromised.