Scanning from source Port 220 for Port 21

[Jamey Dillon <jamey.dillon () comcast net>]

We have in the last 5 weeks seen an increase of scanning from port 220 to FTP. 
The traffic appears to follow the charachteristics of the Dameware scanning of months past.
Has anyone else noticed this on their networks? Do you have any idea what tool/worm may be used to cause this activity?

The traffic is usually 1-5 packets but lately has resulted in up to 55 packets.
See below:
RouterLogs  Mar 29 10:11:39 UTC: %SEC-6-IPACCESSLOGP: list outsiders permitted tcp X.X.139.150(220) -> X.X.230.252(21), 
52 packets 
RouterLogs  Mar 29 10:11:37 UTC: %SEC-6-IPACCESSLOGP: list outsiders permitted tcp X.X.139.150(220) -> X.X.232.251(21), 
52 packets 
RouterLogs  Mar 29 10:11:35 UTC: %SEC-6-IPACCESSLOGP: list outsiders permitted tcp X.X.139.150(220) -> X.X.230.251(21), 
52 packets 
RouterLogs  Mar 29 10:11:22 UTC: %SEC-6-IPACCESSLOGP: list outsiders permitted tcp X.X.139.150(220) -> X.X.232.250(21), 
52 packets 
RouterLogs  Mar 29 10:11:11 UTC: %SEC-6-IPACCESSLOGP: list outsiders permitted tcp X.X.139.150(220) -> X.X.230.250(21), 
52 packets 
RouterLogs  Mar 29 10:11:09 UTC: %SEC-6-IPACCESSLOGP: list outsiders permitted tcp X.X.139.150(220) -> X.X.230.254(21), 
1 packet 
RouterLogs  Mar 29 10:11:06 UTC: %SEC-6-IPACCESSLOGP: list outsiders permitted tcp X.X.139.150(220) -> X.X.230.253(21), 
1 packet 
RouterLogs  Mar 29 10:11:04 UTC: %SEC-6-IPACCESSLOGP: list outsiders permitted tcp X.X.139.150(220) -> X.X.230.248(21), 
52 packets 

Thanks..

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