It is a common fear for people to feel like they are being watched by the federal government. There are a few different signs that may indicate that you are under surveillance, but it is important to keep in mind that not all of these signs necessarily mean that you are being monitored by the feds. In this answer, I will provide some possible indications that the federal government may be watching you, as well as some caveats and ways to protect yourself.

One possible sign that you are under federal surveillance is if you have received a National Security Letter (NSL). NSLs are a tool used by the federal government to obtain information from companies about their customers. They are often accompanied by a gag order, which means that the recipient of the letter is prohibited from disclosing the fact that they received it. If you have received an NSL, it is a strong indication that you are under federal surveillance.
Another possible sign of federal surveillance is if you have noticed an unusual amount of government activity in your neighborhood or around your workplace. This could include an increase in law enforcement or other government officials, or a greater presence of unmarked vehicles. It is important to note, however, that just because you see government activity in your area does not necessarily mean that you are the target of surveillance. There could be other reasons for the increased activity.
If you have been involved in activities that the federal government considers to be suspicious or illegal, such as terrorism, espionage, or drug trafficking, then it is likely that you are under surveillance. The federal government has a number of different tools at its disposal to monitor individuals who are suspected of these types of activities, including wiretaps, physical surveillance, and the use of informants.
Another sign of federal surveillance could be if you have noticed that your phone calls or emails are being monitored. This is particularly true if you have noticed that your phone calls or emails are being interrupted or that there are unusual delays in their delivery. The federal government has the legal authority to monitor communications under certain circumstances, such as when investigating suspected terrorist activities. However, it is important to note that the government is required to obtain a warrant in order to monitor communications, and that there are strict rules and procedures in place to ensure that this power is not abused.
If you are under federal surveillance, you may notice that you are being followed or that you are under physical surveillance. This could include being followed by unmarked vehicles or individuals who appear to be watching you. It is important to note that just because you feel like you are being followed does not necessarily mean that you are under federal surveillance. There could be other reasons for this type of behavior.
It is important to keep in mind that the federal government is not the only entity that may be interested in monitoring your activities. There are a number of other groups, such as private investigators, hackers, and foreign governments, that may also be interested in obtaining information about you. In order to protect yourself from surveillance, it is important to take steps to secure your communications and data.
One way to protect yourself is to use encryption when communicating online. Encryption scrambles your messages so that they can only be read by the intended recipient. There are a number of different tools available for encrypting your communications, such as Signal and PGP.
Another way to protect yourself is to be mindful of the information that you share online. Avoid sharing sensitive information, such as your social security number or bank account information, on social media or other public platforms. Be careful when clicking on links or downloading attachments, as these can be used to install malware or spyware on your device.
In conclusion, there are a number of different signs that may indicate that you are under federal surveillance. These include receiving a National Security Letter, noticing an unusual amount of government activity in your area, being involved in suspicious or illegal activities, having your communications monitored, or being under physical surveillance. However, it is important to keep in mind that not all of these signs necessarily mean that you are under surveillance, and there could be other explanations for the behavior you are seeing.