WebShield does not offer different protection than the other parts of avast, I mean, it uses the same virus signatures, can scan the same infections.
I suggest you run on-demand trojan remover tools:
a-squared
Free AVG Antispyware
SUPERantispyware
Besides this, you can use immunization of SpywareBlaster or Windows Advanced Care (http://www.iobit.com/AdvancedWindowsCarePersonal/index.html).
I suggest Spamihilator (http://www.spamihilator.com/).
Comodo (http://www.personalfirewall.comodo.com/).