Iron-filled carbon nanotubes (Fe-CNT) and iron carbide-filled carbon nanotubes (Fe3C-CNTs) are produced by chemical vapor deposition in a two stage furnace using ferrocene as precursor. The magnetic properties of individual filled CNTs are studied by nano-Hall magnetometry, cantilever magnetometry, and MFM. Fe-CNTs are used to prepare probes for magnetic force microscopy (MFM) by attaching them to the tip of non-magnetic atomic force microscopy cantilevers. Fe-CNTs can be regarded as cylinder shaped single domain nanomagnets that are protected from oxidation by carbon shells. Carbon nanotubes are known to possess both great mechanical stability and elasticity which lead to a much longer lifetime of Fe-CNT MFM probes compared to conventional magnetically coated probes. They exhibit a very high aspect ratio leading to improved topographic imaging on the one hand and better magnetic resolution in MFM on the other hand. In the limit of very long iron nanowires, the lower wire end can be considered as an effective magnetic monopole moment which allows straightforward quantitative stray field measurements. Techniques to manipulate individual Fe-CNTs include removal of carbon shell parts by electron-beam assisted oxidation in humid environment and tailoring the position of the Fe nanowires inside the CNT by controlled application of voltage pulses. Finally, studies exploring the mechanical properties of Fe-CNTs and experiments employing the high magnetic field gradient of Fe-CNTs for magnetic resonance force microscopy will be proposed.