First, please check Gather Proxy scraper and download it.
Open program, in Gather Proxy tab, Select "My URLs" for "Gather proxy from" option.
Create a text file file for custom urls with content as below
http://www.google.com/search?q=google+passed+proxies+#date#+-socks&start=#loop(0,10,10)#&tbs=qdr:d#deep(1)#
http://www.google.com/search?q=scrapebox+proxies+#date#+-socks&start=#loop(0,10,10)#&tbs=qdr:d#deep(1)#
http://www.google.com/search?q=google+passed+proxies+#date-1#+-socks&start=#loop(0,10,10)#&tbs=qdr:d#deep(1)#
http://www.google.com/search?q=scrapebox+proxies+#date-1#+-socks&start=#loop(0,10,10)#&tbs=qdr:d#deep(1)#
http://www.proxyfire.net/forum/forumdisplay.php?f=72#deep(1)##dfil(showthread)#
http://www.blackhatworld.com/blackhat-seo/f103-proxy-lists/#deep(1)##dfil(scrapebox)#
For more details about how to use Gather Proxy scraper and some expression for scrape url please check here
Total proxies:
17948
Alive Proxies (Last checked in past 24 hours):
9762
Total Socks:
3111