Its all done on the quiet because for the most part officially most arab and muslim countries don't recognise Israel's right to exist but Israel does export to them. Until the civil war began even Syria did business one the quiet by buying apples grown by druze in Israel. With weapons there is a very limited products Israel will sell for obvious reasons but when it comes to weapon sales military and security services don't care about politics their priority is getting the right product at the right price. For Israel as long as selling these weapons doesn't affect its own security then profit is priority.
Magnitude 4.2 quake strikes near Grand Coulee Dam in Washington (Reuters)
from the article: Israel selling military wares to Mideast countries, Britain says