Specifications

makes sense to enter something else here if you have chosen ‘replcont’,
‘replabort’, ‘replskip’, or ‘replendskip’ as the action. Click ‘Add’ to gen-
erate the rule and add it to the list field.
To edit a filter rule, select it from the list field by clicking it. The values
are then displayed in the top half of the window. Modify the values
and confirm the changes by clicking ‘Edit’.
To delete filter rules, select them from the list field and click ‘Delete’.
MIME Type Filter
Content filtering on the SuSE Firewall on CD is carried out by the httpf
proxy. Configure it in Figure 3.37 on the facing page. Part of the content fil-
tering is triggered by the tags contained in an HTML page.
Content filtering can take place with the MIME types of documents accessed
from the web over HTTP. These MIME types include, for example, images
(GIF, JPEG, . . .), audio files, (MPEG, WAV, . . . ) or videos (MPEG, AVI, . . . ).
By means of the bit stream transmitted, it can be determined to which MIME
type the requested document belongs. This makes it possible to detect spe-
cific file types and allow or refuse transmission.
If httpf detects a MIME type that is not defined, the object in question is re-
fused. This also makes it possible to determine if the MIME type transmitted
matches the contents transmitted or if, for example, an executable program is
pretending to be a gif image.
Operation
The dialog ‘MIME Type Filter’ shows a list of all MIME types already con-
figured. The three fields ‘MIME type’, ‘Offset’, and ‘String’ are for creating a
new type or editing a Mime type. ‘MIME type’ specifies which MIME type
is involved. Offset refers to the point after the beginning of the file at which
the “string” is located. The two parameters ‘Offset’ and ‘String’ are optional,
because not all file formats can be uniquely identified.
All MIME types intended to pass through the filter must be defined in this
interface. A configuration with most MIME types is contained in the default
template. If you do not want to let certain MIME types through, mark them
and click ‘Delete’. With ‘Next’, continue to the next dialog.
Parent Proxy Configuration
If your provider makes available a specific proxy for HTTP requests, the IP
address of the proxy can be entered in ‘IP address of the parent proxies’.
80 Using the FAS