An easier way is to just not tell the Listserv software about catalist.
This is controlled in the Listserv configuration file.

On Wed, 29 Sep 2004, Wayne T Smith wrote:

>Sounds like you want "Confidential= Yes" on all of your lists.   cheers,
>wayne
>
>Glenda Keyworth wrote:
>
>>We use LISTSERV primarily for internal organizational communications. We have a
>>handful of lists that are open to the public, but the owners are responsible for
>>publicizing them. We don't need or want our lists shown on Catalyst.
>>
>>Catalyst shows many, (but not all) of our LISTSERVs. I would like to prevent
>>Catalyst from showing any of our lists, but I can't find a LISTSERV header
>>keyword or any other method in the manuals, that will prevent Catalyst from
>>seeing our lists.
>>
>>I would prefer to use something in the site-wide configuration to make sure our
>>lists are never picked up by Catalyst, but I would add a keyword to individual
>>list headers to hide them from Catalyst, if necessary. If anyone knows how I can
>>get Catalyst to not even show our organization in Catalyst that would be best.
>>
>>Thank you
>>
>>Glenda Keyworth
>>Austin Community College
>>Austin, Texas
>>
>>
>