X.500 directory service, 519–520. See also Active Directory
XBL (Exploits Block List), 410
.xla files, 202
.xlb files, 202
.xlc files, 202
.xld files, 202
.xlk files, 202
.xll files, 202
.xlm files, 202
.xls files, 202
.xlshtml files, 202
.xlt files, 202
.xlthtml files, 202
.xlv files, 202
.xml files, 202
Xprobe2 fingerprinting tool, 9
.xsl files, 202
XSS (cross-site scripting)
in e-mail, 393
in IE (Internet Explorer), 357–358
malware in, 21