The phrase "various proxies" refers to different substitutes or representatives that are used to stand in for or represent something else. Full definition
They were alleged to have at various times connived and transferred a sum of N2, 899,723,500 from the account of NBC through various proxies for their personal gains. (nigeriapoliticsonline.com)
If you have moral qualms about doing this, you can take out a PO BOX or use various proxy companies in the USA that allow you to use their virtual office as an address. (goodereader.com)
Figure 1: Northern Hemisphere temperature changes estimated from various proxy records shown in blue (Mann 1999). (skepticalscience.com)