CIFS support

File filtering and antivirus scanning for proxy-based inspection on Common Internet File System (CIFS) traffic is supported.

File filtering for CIFS is performed by inspecting the first 4 KB of the file to identify the file's magic number. If a match occurs, CIFS file filtering prevents the CIFS command that contains that file from running.

The CIFS security profile handles the configuration of file filtering on CIFS. The antivirus profile handles the antivirus configuration for CIFS scanning.

For a CIFS profile to be available for assignment in a policy, the policy must use proxy inspection mode. See Proxy mode inspection for details.

The following are not supported by CIFS scanning in proxy inspection mode:

• File types and infections within archive files cannot be detected.
• Oversized files cannot be detected.
• Special condition archive files (encrypted, corrupted, mailbomb, and so on) marked by the antivirus engine are blocked automatically.

Supported file types

File filter supports the following file types:

File Type Name	Description
7z	Match 7-zip files
arj	Match arj compressed files
cab	Match Windows cab files
lzh	Match lzh compressed files
rar	Match rar archives
tar	Match tar files
zip	Match zip files
bzip	Match bzip files
gzip	Match gzip files
bzip2	Match bzip2 files
xz	Match xz files
bat	Match Windows batch files
msc	Match msc files
uue	Match uue files
mime	Match mime files
base64	Match base64 files
binhex	Match binhex files
bin	Match bin files
elf	Match elf files
exe	Match Windows executable files
hta	Match hta files
html	Match html files
jad	Match jad files
class	Match class files
cod	Match cod files
javascript	Match javascript files
msoffice	Match MS-Office files. For example, doc, xls, ppt, and so on.
msofficex	Match MS-Office XML files. For example, docx, xlsx, pptx, and so on.
fsg	Match fsg files
upx	Match upx files
petite	Match petite files
aspack	Match aspack files
prc	Match prc files
sis	Match sis files
hlp	Match Windows help files
activemime	Match activemime files
jpeg	Match jpeg files
gif	Match gif files
tiff	Match tiff files
png	Match png files
bmp	Match bmp files
unknown	Match unknown files
mpeg	Match mpeg files
mov	Match mov files
mp3	Match mp3 files
wma	Match wma files
wav	Match wav files
pdf	Match pdf files
avi	Match avi files
rm	Match rm files
torrent	Match torrent files
msi	Match Windows Installer msi bzip files
mach-o	Match Mach object files
dmg	Match Apple disk image files
.net	Match .NET files
xar	Match xar archive files
chm	Match Windows compiled HTML help files
iso	Match ISO archive files
crx	Match Chrome extension files

Configure file-type filtering and antivirus scanning on CIFS traffic

To configure file-type filtering and antivirus scanning on CIFS traffic:

1. Configure a CIFS domain controller
2. Configure a CIFS profile
3. Configure an antivirus profile

Configure a CIFS domain controller

The domain controller must be configured when CIFS traffic is encrypted, like SMB 3.0 traffic. The configuration tells the FortiGate the network location of the domain controller and the superuser credentials.

To configure the CIFS domain controller:

config cifs domain-controller
    edit "DOMAIN"
        set domain-name "EXAMPLE.COM"
        set username "admin-super"
        set password **********
        set ip 172.16.201.40
    next
end

Configure a CIFS profile

To create a CIFS profile, configure the server credential type and add file filter entries.

Set the CIFS server credential type

The CIFS server credential type can be none, credential-replication, or credential-keytab.

none

The CIFS profile assumes the CIFS traffic is unencrypted (used with SMB 2.0). This is the default value.

config cifs profile
    edit "cifs"
        set server-credential-type none
    next
end

credential-replication

To decrypt CIFS traffic, FortiOS obtains the session key from the domain controller by logging in to the superuser account. The domain controller must be configured.

config cifs profile
    edit "cifs"
        set server-credential-type credential-replication
        set domain-controller "DOMAIN"
    next
end

Variable	Description
domain-controller <string>	The previously configured domain to decrypt CIFS traffic for.

credential-keytab

To decrypt CIFS traffic, FortiOS uses a series of keytab values. This method is used when the SMB connection is authenticated by Kerberos. Keytab entries must be configured, and are stored in FortiOS in plaintext.

config cifs profile
    edit "cifs"
        set server-credential-type credential-keytab
        config server-keytab
            edit "keytab1"
                set keytab "BQIAAABFAAEAC0VYQU1QTEUuQ09NAAdleGFtcGxlAAAAAVUmAlwBABIAILdV5P6NXT8RrTvapcMJQxDYCjRQiD0BzxhwS9h0VgyM"
            next
        end
    next
end

Variable	Description
keytab <keytab>	Base64 encoded keytab file containing the credentials of the server.

Configure CIFS profile file filtering

Multiple file filter entries can be added to a profile.

To configure a file filter entry in a CIFS profile:

config cifs profile
    edit "cifs"
        config file-filter 
            set status {enable | disable}
            set log {enable | disable}
            config entries 
                edit <filter>
                    set comment <string>
                    set action {log | block}
                    set direction {incoming | outgoing | any}
                    set file-type <file_type>
                next
            end
        end
    next
end

Variable	Description
status {enable | disable}	Enable/disable file filter (default = enable).
log {enable | disable}	Enable/disable file filter logging (default = enable).
comment <string>	A brief comment describing the entry.
action {log | block}	The action to take for matched files: log: Allow the content and write a log message (default). block: Block the content and write a log message.
direction {incoming | outgoing | any}	Match files transmitted in the session's originating (incoming) and/or reply (outgoing) direction (default = any).
file-type <file_type>	The file types to be matched (default = none). See Supported file types for details.

Configure an antivirus profile

The antivirus profile handles the antivirus configuration for CIFS scanning.

To configure an antivirus profile:

config antivirus profile
    edit "av"
        ...
        config cifs
            set options {scan avmonitor quarantine}
            set archive-block {encrypted corrupted partiallycorrupted multipart nested mailbomb fileslimit timeout unhandled}
            set archive-log {encrypted corrupted partiallycorrupted multipart nested mailbomb fileslimit timeout unhandled}
            set emulator {enable | disable}
            set outbreak-prevention {disabled | files | full-archive}
        end
    next
end

Variable	Description
options {scan avmonitor quarantine}	Enable/disable CIFS antivirus scanning, monitoring, and quarantine.
archive-block {encrypted corrupted partiallycorrupted multipart nested mailbomb fileslimit timeout unhandled}	Select the archive types to block: encrypted: Block encrypted archives. corrupted: Block corrupted archives. partiallycorrupted: Block partially corrupted archives. multipart: Block multipart archives. nested: Block nested archives. mailbomb: Block mail bomb archives. fileslimit: Block exceeded archive files limit. timeout: Block scan timeout. unhandled: Block archives that FortiOS cannot open.
archive-log {encrypted corrupted partiallycorrupted multipart nested mailbomb fileslimit timeout unhandled}	Select the archive types to log: encrypted: Log encrypted archives. corrupted: Log corrupted archives. partiallycorrupted: Log partially corrupted archives. multipart: Log multipart archives. nested: Log nested archives. mailbomb: Log mail bomb archives. fileslimit: Log exceeded archive files limit. timeout: Log scan timeout. unhandled: Log archives that FortiOS cannot open.
emulator {enable | disable}	Enable/disable the virus emulator (default = enable).
outbreak-prevention {disabled | files | full-archive}	Enable the virus outbreak prevention service: disabled: Disabled (default). files: Analyze files as sent, not the content of archives. full-archive: Analyze files, including the content of archives.

Log examples

File-type detection events generated by CIFS profiles are logged in the utm-cifs log category. Antivirus detection over the CIFS protocol generates logs in the utm-virus category. See the FortiOS Log Message Reference for more information.

Logs generated by CIFS profile file filter:

date=2019-03-28 time=10:39:19 logid="1800063001" type="utm" subtype="cifs" eventtype="cifs-filefilter" level="notice" vd="vdom1" eventtime=1553794757 msg="File was detected by file filter." direction="incoming" action="passthrough" service="CIFS" srcip=10.1.100.11 dstip=172.16.200.44 srcport=33372 dstport=445 srcintf="wan2" srcintfrole="wan" dstintf="wan1" dstintfrole="wan" policyid=1 proto=16 profile="cifs" filesize="1154" filename="virus\\test.png" filtername="2" filetype="png"

date=2019-03-28 time=10:39:12 logid="1800063001" type="utm" subtype="cifs" eventtype="cifs-filefilter" level="notice" vd="vdom1" eventtime=1553794751 msg="File was detected by file filter." direction="incoming" action="passthrough" service="CIFS" srcip=10.1.100.11 dstip=172.16.200.44 srcport=33370 dstport=445 srcintf="wan2" srcintfrole="wan" dstintf="wan1" dstintfrole="wan" policyid=1 proto=16 profile="cifs" filesize="81975" filename="virus\\screen.png" filtername="2" filetype="png"

date=2019-03-28 time=10:33:55 logid="1800063000" type="utm" subtype="cifs" eventtype="cifs-filefilter" level="warning" vd="vdom1" eventtime=1553794434 msg="File was blocked by file filter." direction="incoming" action="blocked" service="CIFS" srcip=10.1.100.11 dstip=172.16.200.44 srcport=33352 dstport=445 srcintf="wan2" srcintfrole="wan" dstintf="wan1" dstintfrole="wan" policyid=1 proto=16 profile="cifs" filesize="28432" filename="filetypes\\mpnotify.exe" filtername="3" filetype="exe"

date=2019-03-28 time=10:33:45 logid="1800063000" type="utm" subtype="cifs" eventtype="cifs-filefilter" level="warning" vd="vdom1" eventtime=1553794424 msg="File was blocked by file filter." direction="incoming" action="blocked" service="CIFS" srcip=10.1.100.11 dstip=172.16.200.44 srcport=33348 dstport=445 srcintf="wan2" srcintfrole="wan" dstintf="wan1" dstintfrole="wan" policyid=1 proto=16 profile="cifs" filesize="96528" filename="filetypes\\winmine.exe" filtername="3" filetype="exe"

Logs generated by AV profile for infections detected over CIFS:

date=2019-04-09 time=15:19:02 logid="0204008202" type="utm" subtype="virus" eventtype="outbreak-prevention" level="warning" vd="vdom1" eventtime=1554848342519005401 msg="Blocked by Virus Outbreak Prevention service." action="blocked" service="SMB" sessionid=177 srcip=10.1.100.11 dstip=172.16.200.44 srcport=37444 dstport=445 srcintf="wan2" srcintfrole="wan" dstintf="wan1" dstintfrole="wan" policyid=1 proto=6 direction="incoming" filename="outbreak\\zhvo_test.com" quarskip="File-was-not-quarantined." virus="503e99fe40ee120c45bc9a30835e7256fff3e46a" dtype="File Hash" filehash="503e99fe40ee120c45bc9a30835e7256fff3e46a" filehashsrc="fortiguard" profile="av" analyticssubmit="false" crscore=50 craction=2 crlevel="critical"

date=2019-04-09 time=15:18:59 logid="0211008192" type="utm" subtype="virus" eventtype="infected" level="warning" vd="vdom1" eventtime=1554848339909808987 msg="File is infected." action="blocked" service="SMB" sessionid=174 srcip=10.1.100.11 dstip=172.16.200.44 srcport=37442 dstport=445 srcintf="wan2" srcintfrole="wan" dstintf="wan1" dstintfrole="wan" policyid=1 proto=6 direction="incoming" filename="sample\\eicar.com" quarskip="File-was-not-quarantined." virus="EICAR_TEST_FILE" dtype="Virus" ref="http://www.fortinet.com/ve?vn=EICAR_TEST_FILE" virusid=2172 profile="av" analyticscksum="275a021bbfb6489e54d471899f7db9d1663fc695ec2fe2a2c4538aabf651fd0f" analyticssubmit="false" crscore=50 craction=2 crlevel="critical"