The named categories are consistent: buying or selling links that pass ranking signals, excessive reciprocal exchanges, large-scale article marketing with keyword-rich anchors, automated link generation, and private blog networks. Detection is imperfect, which is why the tactics persist, and the asymmetry is the argument against them — the gain is a ranking obtainable another way, the loss is a manual action and months of recovery.
If you inherit a bad profile, the modern advice is less dramatic than it used to be: Google discounts most spam links automatically, and the disavow file is a tool of last resort for sites with a confirmed manual action. Spending the same budget on a genuinely linkable asset is nearly always the better trade.