In the present paper we show that the Levy-Ito representation of the infinitesimal generator $L$ for Levy processes $X_t$ can be written in a convolution-type form. Using the obtained convolution form we have constructed the quasi-potential operator $B$. We denote by $p(t,Δ)$ the probability that a sample of the process $X_t$ remains inside the domain $Δ$ for $0{\leq}τ{\leq}t$ (ruin problem). With the help of the operator $B$ we find a new formula for $p(t,Δ)$. This formula allows us to obtain long time behavior of $p(t,Δ)$.