I use s/\0+//g right now and it seems to work fine. Where do I get those strings? They come on the socket I am listening to. String are generated by a phone switch. NULL characters are always added whenever the date is inserted in a string like in the example bellow:

120507 1324 01300            6417                  13639820545  801<CR
+><LF>13:24 12/05<CR><LF>^@^@^@13:24 12/05<CR><LF>^@^@^@120507 1324 00
+456      2867416007  808             14972681971  801<CR><LF>13:24 12
+/05<CR><LF>^@^@^@
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I don't see any other places with those characters (not in the data I am capturing, or anywhere else), only when the timestamp is added in string. I guess it is safe to use s/\0+//g in this case, am I right?