One of our three PCs running Windows 7 has malware running that destroys our Firefox browsing experience on our favorite news sites, including realclearpolitics.com, wsj.com, cnn.com, and nbcnews.com, though not abcnews.com or cbsnews.com. The two others and a fourth machine running Windows 8 are unaffected. We believe that the malicious software was installed on the one machine when we erroneously upgraded Firefox from a non-Mozilla source a year or so ago. Like this user (https://support.mozilla.org/en-US/questions/1090273), our Internet Explorer is completely unaffected. For the present we have quit running Firefox on the affected machine. It is completely unusable for those sites. I am posting this with Firefox on one of the unaffected computers. Firefox is completely hijacked on affected sites. It is fine as long as an affected website isn't accessed. Once one is accessed, the malicious behavior begins. The page is initially displayed normally, but then Firefox begins autonomously accessing a steady stream of suspect sites. The browser nearly freezes, but continues to function slowly. Mousing over any link shows that clicking will access the target through another site, presently s.klmtm2k6.com. An earlier manifestation involved "ads by name" and "dns unlocker". After we got rid of those maniifestations, the problem morphed into the current form. Clicking a redirected link brings up one of a myriad of malicious sites that often try to sell us software to fix such problems. In that sense, it appears to be a mild form of ransomware. I have tried many things to rid Firefox of this malware. Last weekend, I removed all plug-ins and extensions, deleted the Firefox profile, and did a clean install of the 64-bit US English version from https://www.mozilla.org/en-US/firefox/all/. I downloaded the install set on one of my clean machines and moved it to the infected machine using my local area network. I did not use the infected Firefox to do the download, nor did I use the Firefox downloader/updater stub. I did two full system scans using Bitdefender, and found some infected Firefox executables in the Mozilla/Old Firefox and Mozilla/OldFirefox directories that I had renamed from Mozilla/FireFox during earlier efforts to clear up this problem. I fixed all problems except reported concerns with those "password protected" files that turned out to be Windows System Restore Points to which Bitdefender could not gain access. I'll eventually delete those, but for now I've left them alone. Meanwhile, we still have the problem. This is not the first time I have tried to solve the problem. In April 2015, I followed instructions I found here (https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware), and downloaded and ran a handful of different anti-malware and anti-virus scanning and removal programs. None of them helped at all. Last September, I again googled for solutions and tried some of them. My purpose in posting here is to share my experience with others. At this point, I am turning to BleepingComputer.com for help. Searching there for "firefox hijacker malware" has shown me logs of assistance provided to others to remove similar problems. I am hopeful. I'll report back on my results.