  We investigate drag force in a thermal plasma of N=4 super Yang-Mills theory
via both fundamental and Dirichlet strings under the influence of non-zero NSNS
$B$-field background. In the description of AdS/CFT correspondence the endpoint
of these strings correspondes to an external monopole or quark moving with a
constant electromagnetic field. We demonstrate how the configuration of string
tail as well as the drag force obtains corrections in this background.
