If you notice the presence of Satan in the prayer, say this dua and spit three times on the left side -

أَعُوْذُ بِاللَّهِ مِنَ الشَّيْطَانِ الرَّجِيمِ

A‛oodhu billaahi minash-Shaytaanir-rajeem

I seek refuge in Allah from Satan the outcast.

Reference: Muslim: 2203