  In this paper, we analyze the secrecy outage performance for more realistic
eavesdropping scenario of free-space optical (FSO) communications, where the
main and wiretap links are correlated. The FSO fading channels are modeled by
the well-known M\'alaga distribution. Exact expressions for the secrecy
performance metrics such as secrecy outage probability (SOP) and probability of
the non zero secrecy capacity (PNZSC) are derived, and asymptotic analysis on
the SOP is also conducted. The obtained results reveal useful insights on the
effect of channel correlation on FSO communications. Counterintuitively, it is
found that the secrecy outage performance demonstrates a non-monotonic behavior
with the increase of correlation. More specifically, there is an SNR penalty
for achieving a target SOP as the correlation increases within some range.
However, when the correlation is further increased beyond some threshold, the
SOP performance improves significantly.
