If your phone's battery life suddenly starts draining much faster than usual, it could be a sign of malicious software running in the background, potentially from spyware.
Excessive data usage that can't be explained by your regular activities may indicate that some unauthorized processes are running on your phone, possibly as a result of tapping.
If you hear strange background noises, like clicking, static, or echoes during your phone conversations, it could be a sign of interference or tapping.
If your phone takes longer to shut down or restart than usual, it might be due to unwanted software or monitoring apps that need time to close.