Yes, lone wolves can certainly be stopped. They are the people who used to belong to a group (in this case, terrorists) but now they act alone to become stronger (in this case, for easier action). Their plans are usually not considered from different perspectives, as there are no one else to offer opinions for them, so they may have many loopholes and as such, with close surveillance, we can detect loopholes in suspicious activities to stop them before it's too late.
"Lone wolves," or terrorists that act alone without the explicit support of an organization such as ISIS, are virtually impossible to stop. This is the determination of law enforcement agencies such as the FBI. The individual may become disaffected with living in the United States, and he may not have visited outside the country.
No, there is no way to completely eradicate "lone wolves." Although safety protocols can significantly decrease the likelihood that a "lone wolf" will have the ability to attack, they cannot be stopped. A "lone wolf," by definition, is someone who works alone. It is difficult to find these individuals because they are less likely to have set off alerts on social media sites. Security protocols, such as metal detectors, may hinder a person's ability to attack. However, where there is a will, there is a way. There is no way to account for all possible scenarios, and at some point, another "lone wolf" will attack.
When people decide to launch an attack or attacks against society, they are difficult to stop. It is not difficult to target unarmed people as they go about their daily lives. Most people are focused on working and enjoying time with family and friends, not watching for terrorist attacks. Lone wolves know this and exploit the vulnerability.