Which statement is true of application$-$filtering firewalls?

a$.$ They Are Less Secure Than Packet$-$Filtering Firewalls

b$.$ They Filter Viruses Less Effectively Than Packet$-$Filtering Firewalls

c$.$ They Are More Expensive Than Packet$-$Filtering Firewalls

d$.$ They Filter Faster Than Packet$-$Filtering Firewalls